Wire in _EXTRA_INSTALL_OPTS...

Updates the various environment.d elements so that we can control
with a high level of granularity whether we enable
--system-site-packages in our virtualenvs. At a high level
OPENSTACK_EXTRA_INSTALL_OPTS can be set to -s to allow
os-svc-install to enable --system-site-packages globally.
The per element environment variables if set will override this
setting.

A step towards supporting both isolated and global venvs
for OpenStack elements installed from git source.

Change-Id: Ic3dc42717a90f02a58af345c5564336b64f930e4
mysql-common requires python MySQLdb

The 50-mysql-users script requires MySQLdb to function

Change-Id: I0ce5ef8e9995bce6fbbc6abbffde9109bb3a01d2
Merge "Wire in _EXTRA_INSTALL_OPTS..."