This change adds a new hook to Manager class called init_host_with_rpc()
to allow services like scheduler to do something once RPC is ready.
Copied from cinder 65fa80c361
and 60c563f72d
Change-Id: Iac6507a6e395c55f0fec453650009f08c2bb6563
Closes-Bug: #1271568
(cherry picked from commit 0339802a5d)
(cherry picked from commit 887c4bf4c0)