Add unique constraint to ConsolePool.

Added unique constraint to ConsolePool model
`uniq_console_pools0host0console_type0compute_host0deleted` ('host',
'console_type', 'compute_host', 'deleted').
Added new exception `ConsolePoolExists`. Function `console_pool_create`
updated. Tests updated respectively.

blueprint db-enforce-unique-keys
Fixes bug 1185450

Change-Id: I095a52f2d21ec48b079e61034d80bcb9e7fcab79
Revert "Sync latest rpc changes from oslo-incubator"

Fixes bug #1200069

Looks like there's a serious issue with the kombu heartbeat implementation.

This reverts commit 386a8c21ec6acbaa059eabd166dbf7feea2fad7d

Change-Id: I354f5e3c5af110542a3c25d117b14e7be02f169b
Merge "Add unique constraint to ConsolePool."
Merge "Revert "Sync latest rpc changes from oslo-incubator""
Merge remote-tracking branch 'm_src_repo/citrix-fixes' into build-temp