[BUG] Incorrect log rate metrics emitted by executor

Current behavior

Starting with Diego Release v2.139.0, the app log rate metric is emitted twice: once as 0 and once as the actual value.

Reproduction steps:

❯ cf push noisy-app -b binary_buildpack -m 64M -u process -c "while true; do echo 'Generating constant log traffic to establish a non-zero log rate'; sleep 0.1; done"

Prior to Diego v2.139.0:

❯ cf tail noisy-app -f -c metric | grep log_rate

   2026-08-12T12:09:23.86-0700 [noisy-app/0] GAUGE log_rate:631.466667 B/s
   2026-08-12T12:09:23.86-0700 [noisy-app/0] GAUGE log_rate_limit:-1.000000 B/s
   2026-08-12T12:09:38.86-0700 [noisy-app/0] GAUGE log_rate:631.466667 B/s
   2026-08-12T12:09:38.86-0700 [noisy-app/0] GAUGE log_rate_limit:-1.000000 B/s

Starting with Diego v2.139.0:

❯ cf tail noisy-app -f -c metric | grep log_rate

   2026-08-12T12:58:06.01-0700 [noisy-app/0] GAUGE log_rate:0.000000 B/s
   2026-08-12T12:58:06.01-0700 [noisy-app/0] GAUGE log_rate_limit:0.000000 B/s
   2026-08-12T12:58:13.06-0700 [noisy-app/0] GAUGE log_rate_limit:-1.000000 B/s
   2026-08-12T12:58:13.06-0700 [noisy-app/0] GAUGE log_rate:631.466667 B/s
   2026-08-12T12:58:21.01-0700 [noisy-app/0] GAUGE log_rate:0.000000 B/s
   2026-08-12T12:58:21.01-0700 [noisy-app/0] GAUGE log_rate_limit:0.000000 B/s
   2026-08-12T12:58:28.06-0700 [noisy-app/0] GAUGE log_rate:631.466667 B/s
   2026-08-12T12:58:28.06-0700 [noisy-app/0] GAUGE log_rate_limit:-1.000000 B/s

Note the log_rate:0.000000 B/s in addition to the actual value.

Visible via CAPI/CLI (edited for clarity):

❯ while 1; do; cf app noisy-app; done
~/workspace/cf-deployment
direnv: loading ~/workspace/cf-deployment/.envrc
direnv: export +PROJECT_DIR
Showing health and status for app noisy-app in org org / space space as admin...

name:              noisy-app
requested state:   started
routes:            noisy-app.fa6482e64d.shepherd.tanzu.broadcom.net
last uploaded:     Wed 12 Aug 12:02:46 PDT 2026
stack:             cflinuxfs4
buildpacks:
	name               version   detect output   buildpack name
	binary_buildpack   1.1.21    binary          binary

type:           web
sidecars:
instances:      1/1
memory usage:   64M
     state     since                  cpu    memory         disk          logging               cpu entitlement   details   ready
#0   running   2026-08-12T19:56:15Z   1.6%   10.9M of 64M   39.7M of 1G   631B/s of unlimited   647.1%                      true
~/workspace/diego-release
direnv: unloading
Showing health and status for app noisy-app in org org / space space as admin...

name:              noisy-app
requested state:   started
routes:            noisy-app.fa6482e64d.shepherd.tanzu.broadcom.net
last uploaded:     Wed 12 Aug 12:02:46 PDT 2026
stack:             cflinuxfs4
buildpacks:
	name               version   detect output   buildpack name
	binary_buildpack   1.1.21    binary          binary

type:           web
sidecars:
instances:      1/1
memory usage:   64M
     state     since                  cpu    memory         disk          logging               cpu entitlement   details   ready
#0   running   2026-08-12T19:56:15Z   1.6%   10.9M of 64M   39.7M of 1G   631B/s of unlimited   647.1%                      true

[...]

~/workspace/diego-release
direnv: unloading
Showing health and status for app noisy-app in org org / space space as admin...

name:              noisy-app
requested state:   started
routes:            noisy-app.fa6482e64d.shepherd.tanzu.broadcom.net
last uploaded:     Wed 12 Aug 12:02:46 PDT 2026
stack:             cflinuxfs4
buildpacks:
	name               version   detect output   buildpack name
	binary_buildpack   1.1.21    binary          binary

type:           web
sidecars:
instances:      1/1
memory usage:   64M
     state     since                  cpu    memory         disk          logging        cpu entitlement   details   ready
#0   running   2026-08-12T19:56:15Z   1.6%   10.9M of 64M   39.7M of 1G   0B/s of 0B/s   637.1%                      true
~/workspace/cf-deployment
direnv: loading ~/workspace/cf-deployment/.envrc
direnv: export +PROJECT_DIR
Showing health and status for app noisy-app in org org / space space as admin...

name:              noisy-app
requested state:   started
routes:            noisy-app.fa6482e64d.shepherd.tanzu.broadcom.net
last uploaded:     Wed 12 Aug 12:02:46 PDT 2026
stack:             cflinuxfs4
buildpacks:
	name               version   detect output   buildpack name
	binary_buildpack   1.1.21    binary          binary

type:           web
sidecars:
instances:      1/1
memory usage:   64M
     state     since                  cpu    memory         disk          logging        cpu entitlement   details   ready
#0   running   2026-08-12T19:56:14Z   1.6%   10.9M of 64M   39.7M of 1G   0B/s of 0B/s   637.1%                      true

[...]

Desired behavior

Restore the behavior prior to Diego Release v2.139.0

Affected Version

v2.139.0

Start by reproducing the issue with the provided cf push command and inspect the executor's log-rate metric emission path. Compare the output with the v2.139.0 examples; done means the duplicate zero-valued metrics are gone and behavior matches the pre-v2.139.0 output.