Call nodetool drain before stopping cassandra
Call nodetool drain before stopping cassandra

It was observed that some of the commit logs were corrupted
during upgrade and there exists a window after installing
cassandra that clients can connect to it and can generate
commit logs. Hence added nodetool drain before stopping
cassandra so that commit logs are flushed to SSTables.

Change-Id: I2e5649ec6e62f17bc9a67765395e2313dbe140ca
Closes-Bug: #1672894

Juniper/contrail-provisioning,Juniper/contrail-provisioning