beta: symlink /a/common

The multiversion/defines.php does use /a/common which is not existing on
the beta cluster.  This patch makes it a symbolic link to the shared
directory.

That also makes puppet ensure /a/common exists in production.

On labs, define /data/project/apache and
/data/project/apache/common-local as belonging to mwdeploy:mwdeploy

Change-Id: Iaf19f0e8cf029cdbbbb2dabe3ae1d07cee417c39