engine: Disable iSCSI multipathing for datacenters < 3.4

I had to fix a few issues in VDSM 3.4 in order to support configuration of
iSCSI multipathing, therefore this feature should be disabled for earlier
datacenter versions.

Change-Id: I623cd917ca0871a9d3d09c2d30ec2dfc114d383e
Signed-off-by: Sergey Gotliv <sgotliv@redhat.com>
engine: Send ifaceName and tpgt in connectStorageServer

Engine mistakenly sent initiatorName instead of ifaceName which overwrote
existing initiatorName configured in the host. Wrong initiatorName caused
host fail to perform iSCSI connection.

In case of tpgt the problem is terminology. Engine sent it as a "portal"
and its value is integer,  but from the iSCSI perspective portal is an
access point to one or more targets, while this integer actually
represents a tpgt - target portal group tag which is numeric representation
of which IP addresses a target is allowed to bind on.

Bug-Url: https://bugzilla.redhat.com/1078137
Change-Id: Ife467feb8aad9711da5d6a5df305e50fe6bf51e9
Signed-off-by: Sergey Gotliv <sgotliv@redhat.com>
engine: Set default tpgt value to 1

Engine uses wrong iSCSI terminology, portal instead of tpgt (target
portal group tag) which only purpose at this stage impose iSCSI layer to
create node record in the new format supporting multipathing.

Tpgt default value in VDSM is 1 so it should be the same here.

Change-Id: I7ebfc1335b051e02f62b9544d2500416818940d0
Signed-off-by: Sergey Gotliv <sgotliv@redhat.com>