Restrict top output to container's pids only

Due to the way ps arguments work, it was possible to display pids
that dont below to the container in top output. We now filter pids
that dont belong to the container out of the output.  This also means
the pid column must be present in the output or we throw an error.

This resolves issue #391
Signed-off-by: baude <bbaude@redhat.com>

Closes: #400
Approved by: rhatdan
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f