Check for the SHARD Status before opening the OVSDB port/HwvtepSouthboundProvider...

Check for the SHARD Status before opening the OVSDB port/HwvtepSouthboundProvider intialization.

JIRA: OVSDB-484

Currently the HwvtepSouthboundProvider is intialized and the Ovsdb port is opened.
As soon as the Ovsdb port is opened the tors will connected to the HwvtepSouthboundPlugin.
The HwvtepSouthboundPlugin will process the connected tors and tries to build the topology operational
and further the topology config and tries to update these datastores.
If the topology SHARDs are not up or the SHARD leaders are not elected by this time, it ends up in the
exceptions while updating the datastores and the operational and config datastores will not be populated
with the expected data.

The fix is check for the topology config and operational SHARDs status up and Leaders for these are
elected and then initialize HwvtepSouthboundProvider and start Ovsdb port when they are up.

Signed-off-by: Chandra Shekar S <chandra.shekar.s@ericsson.com>
Change-Id: Ia8599b9ed9cc3d5afbdb29a951cebee01c15ddbe