Support iSER driver within the ISCSITarget flow

Support iSER driver within the ISCSITarget flow

Currently the iSER driver is supported over TGT only,
and there are a couple of iSER classes that inherits
from iSCSI classes, but most of their functionality is
the same as the iSCSI classes. This code duplication caused
instability in the iSER driver code, when new features or
changes are added to the iSCSI driver flow.

Main changes:
  1. Added a new parameter to volume/driver.py in order to
     set the iSCSI protocol type to 'iscsi' or 'iser', with default
     to 'iscsi'.
  2. Configured TGT VOLUME_CONF and VOLUME_CONF_WITH_CHAP_AUTH
     with the new iSCSI protocol parameter.
  3. Added support for RDMA (using iSER) to cinder-rtstool.
  4. Set "driver_volume_type" to "iscsi" or "iser" value, according
     to the new parameter value.
  5. Added unit tests for the new iSER flow.
  6. Added deprecation alert to ISERTgtAdm.

DocImpact

Implements: blueprint support-iscsi-driver

Change-Id: Ie2c021e7fd37e7221f99b3311e4792c958045431