flag provided but not defined: -environment

[carsonip]

APM Server version (apm-server version): 8.x branch, 9.0 branch

Description of the problem including expected versus actual behavior:

On startup, apm-server will fail to start if --environment is passed. This causes docker images to fail as the entrypoint runs apm-server with --environment=container.

Steps to reproduce:

Please include a minimal but complete recreation of the problem,
including server configuration, agent(s) used, etc. The easier you make it
for us to reproduce it, the more likely that somebody will take the time to
look at it.

1. go run ./x-pack/apm-server --environment=container -e

Provide logs (if relevant):

flag provided but not defined: -environment
Usage of /tmp/go-build943970858/b001/exe/apm-server:
  -E value
        Configuration overwrite
  -N    Disable actual publishing for testing
  -c value
        Configuration file, relative to path.config (default beat.yml)
  -cpuprofile string
        Write cpu profile to file
  -httpprof string
        Start pprof http server
  -memprofile string
        Write memory profile to this file
  -path.config value
        Configuration path
  -path.data value
        Data path
  -path.home value
        Home path
  -path.logs value
        Logs path
  -plugin value
        Load additional plugins
  -strict.perms
        Strict permission checking on config files (default true)
exit status 2

[carsonip]

git bisect shows that the bad commit is 7efa6d5 which is from #14214

[carsonip]

Closing as #14292 and its 8.x backport #14314 are merged.