netconfig.managed forces base enviroment as default

Description of Issue

netconfig.managed forces the use of base as the default for saltenv. this if you aren't looking for it can cause problems if you are planning to use netconfig.managed inside an environment and forget to specify - saltenv: {{saltenv}} in the stanza.

Setup

setup netconfig.managed in a different environment with the template file in that same environment. but don't include a saltenv line in the stanza.

Steps to Reproduce Issue

Use the above setup and run a highstate on the proxy minion with --saltenv=your_enviroment
Watch as the template is tried to be pulled from base and fails.

Versions Report

(Provided by running salt --versions-report. Please also mention any differences in master/minion versions.)
This looks like saltenv was changed from None to base in 2019.2.0 in the code. It should most likely be returned to None.

Start at the netconfig.managed entry point and inspect the saltenv handling, especially the change introduced in 2019.2.0. Reproduce the highstate with --saltenv=your_environment and a template in that environment; done means the template lookup uses the selected environment when no saltenv is specified in the stanza.