Fixed Neutron ML2 issues

- Value of CONFIG_NEUTRON_ML2_VXLAN_GROUP is missing quotes which generates
Puppet syntax error when it is used

- Command 'neutron-db-manage upgrade' is run only on certain host, so race
condition has to be set only on relevant host

- In case of multihost installation Neutron API has to be available for OSCLIENT_HOST
and HORIZON_HOST

Fixes: rhbz#1066519, rhbz#1068962
Closes-bug: 1288447

Change-Id: I40a7cd0c3117152eac945ab26bf0b51e911a4765
(cherry picked from commit 7f536f7e51bbb27a9a3cadb7a5ca73aeb10c190e)
Merge "Fixed Neutron ML2 issues" into havana