Keep pid of salt CLI command from showing in status.pid output

When status.pid is executed by the salt-minion instance running on the
master, it also returns the pid of the salt CLI command, because the
search string matches. This commit adds another grep to the ps/grep/awk
one-liner, which filters out lines matching 'status.pid'.
Merge pull request #9025 from terminalmage/issue8720

Keep pid of salt CLI command from showing in status.pid output