Correct SELinux file contexts

OpenStack components installed via source are placed under
/opt/stack/venvs. The files under /opt/stack/venvs/<component>/bin
do not have the correct SElinux file contexts. This change
applies the same context as they would have received if they had
been installed by a rpm package under /usr/bin.

Closes-Bug: 1340499
Change-Id: Ibffa1b986b52a1dc28de8d3b8056eed92aae9ee7
Merge "Correct SELinux file contexts"