This change add a min value of 1 to
[oslo_messaging_rabbit]/rpc_conn_pool_size
such that there is always at least 1 connection avaiable.
This change add a runtime check to ensure that
[oslo_messaging_rabbit]/rpc_conn_pool_size is greater than
or equal too [oslo_messaging_rabbit]/conn_pool_min_size
Change-Id: I2ad4b9f1d012c9f0586a932ac27d96da1bcc4e4c
Closes-Bug: #1899533