Simplify delete_health_monitor() using cascades

Currently delete_health_monitor() emulates behaviour of
cascade deletion: when a HealthMonitor instance is deleted,
all corresponding PoolMonitorAssociations are queried and
deleted one by one. This can be done automatically by means
of SQLAlchemy if we set proper cascade flags on the relationship
between HealthMonitor and PoolMonitorAssociations models.

Fixes bug 1169107.

Change-Id: I674c381192719a56433f67be53a32203c36ebe2b
Create veth peer in namespace.

 * Update veth pair creation to set the namespace of the peer
   device on creation rather than subsequently adding it to the
   namespace.
 * This change supports kernels with limited namespace support
   (e.g. RHEL 6.5) so long as ovs_use_veth is set to True.
 * Addresses bug 1171727

Change-Id: I1885acc9934e7627bb9872703df7f5edf2980722
Imported Translations from Transifex

Change-Id: I9d2a1a68d17f4b11e338f84d40f7ae3d0b7ffa04
Merge "Create veth peer in namespace."
Merge "Imported Translations from Transifex"
Merge "Simplify delete_health_monitor() using cascades"