[BUG] salt-master wastes time writing event data to standard out when executing runner functions through the api

Description
I was doing some profiling to try and understand why some of my salt api requests were so slow and I noticed that the salt-master spends some considerable time in display_output printing data to standard out, which for me is /dev/null.

I've worked around this by setting quiet: True in my salt master configuration. But this doesn't seem to be documented anywhere.

In addition I notice that when the RunnerClient is constructed in salt.master.Maintenance._post_fork_init quiet is forced to True, but when the runner client used by the api is constructed in salt.master.ClearFuncs.runner it isn't. I wonder if it should be.

Versions Report

Salt Version:
           Salt: 3001

Dependency Versions:
           cffi: 1.11.5
       cherrypy: unknown
       dateutil: Not Installed
      docker-py: Not Installed
          gitdb: Not Installed
      gitpython: Not Installed
         Jinja2: 2.10.1
        libgit2: Not Installed
       M2Crypto: Not Installed
           Mako: 1.0.9
   msgpack-pure: Not Installed
 msgpack-python: 0.5.6
   mysql-python: Not Installed
      pycparser: 2.14
       pycrypto: Not Installed
   pycryptodome: 3.9.8
         pygit2: Not Installed
         Python: 3.6.8 (default, Mar 21 2019, 10:08:12)
   python-gnupg: Not Installed
         PyYAML: 5.1
          PyZMQ: 17.0.0
          smmap: Not Installed
        timelib: Not Installed
        Tornado: 4.5.3
            ZMQ: 4.1.6

System Versions:
           dist: fedora 28 Twenty Eight
         locale: utf-8
        machine: x86_64
        release: 4.7.10
         system: Linux
        version: Fedora 28 Twenty Eight

Start in salt.master.Maintenance._post_fork_init and salt.master.ClearFuncs.runner, then trace how RunnerClient handles quiet and how display_output writes event data to standard output. Compare the two construction paths and verify that API runner calls no longer spend time writing event data to stdout while preserving the documented quiet configuration behavior.