LVM: update iscsi target on volume attach

This patch updates the existing iSCSI target for a LVM volume during
attach.  This is necessary in the event that a user extended the volume
after creation so that the correct size is visible to the host.

This adds support only for tgtadm.  Other changes may be needed for
ietadm/lioadm to provide the same functionality.

Change-Id: I185a90ffc4d50dd9f91381df07289476fa792043
Closes-Bug: #1248415
Remove legacy config option 'connection_type'

'connection_type' is a legacy config option originated from Nova.
Nova used this option to specify underlying virtualization type for
compute service and had deprecated it (with 'compute_driver') in
Folsom and had it removed in later release.  In Cinder Folsom release,
the XenSMDriver in Cinder used this config option to verify the target
hypervisor but in Grizzly XenSMDriver has been renamed and refactored
and no longer used this config.  Therefore, this option is dead for
a long time, and should be removed.

Change-Id: I4d72f31302fa813df42e71224151148a9c4a76c7
Use a *args pass-in instead of a list one

Change-Id: Ieef972f413dcf444d26c15a02d1993acf7cbb079
Merge "LVM: update iscsi target on volume attach"
Merge "Use a *args pass-in instead of a list one"
Merge "Remove legacy config option 'connection_type'"