fix ttcn3-bsc-test under CentOS: install missing osmo-bts-omldummy
In binary packages for Debian, osmo-bts-omldummy is (for some reason) part of 'osmo-bts-virtual' package. For CentOS this binary is shipped properly in a separate package, so let's install it.
This change fixes ttcn3-bsc-test under CentOS failing with:
/usr/local/bin/respawn.sh: line 9: osmo-bts-omldummy: command not found
