Add additional metadata as key-value pairs in 3PAR

Track status of openstack volumes on 3PAR through
additional metadata added as key-value pairs. During volume attach
and detach, corresponding instance metadata is updated onto the
cinder volumes.

Change-Id: Iea8d2f26555e6be60001bf73755cae42446afec6
Closes-Bug: #1258033
Merge "Add additional metadata as key-value pairs in 3PAR"