Add ability to zfssa driver to create multiple initiator groups

Currently the zfssa driver only support one initiator group. This
is causing broken scsi devices when detaching volumes from instances.
This fix adds support for configuring multiple initiator groups.

Closes-Bug: #1378390
DocImpact

Change-Id: Ib3262ebd40e9c2ff2f36d0a7b1b5b3506ed3acc1
Merge "Add ability to zfssa driver to create multiple initiator groups"