VolumeManager: initialize even if a volume can't be found

If a previously volume cannot be exported (for example, because
an iSCSI target's backing LV is no longer present), VolumeManager
would previously bail out, leaving the volume service uninitialized.
This left volumes dangling in limbo: their state would be reported
as available (clearly not a reflection of reality), and they could
not be deleted (because the volume service that would be responsible
for deletion was unavailable).

Instead, catch an exception raised by ensure_export() separately,
log it, and set the volume to the error state.

For the tgt backend, this will also remove the volume_path file.
Previously this would cause an ISCSITargetRemoveFailed exception
when the volume would be removed. Instead, simply log a warning
and return, the way other backends (example: RBD) already do.

Also, add an info message that reflects the actual path and
contents of the volume_path file.

Finally, fix up the tgtadm unit test so that it tests for
identical IQNs,

Closes-bug: 1270959.

Change-Id: Id61407c9a5e020d5a823dd7b8c973d237c35cb9b
Revert initialize_connection changes

A change was merged that reusulted in interittent
gate failures.  It seems that in certain cases the
intitialize is doing an update targets and is
deleting the existing targets and not recreating them.

The idea of this patch was to fix up the iscis targets
for cases where volumes are extended.

A better solution is in progress that will remove the
target creation from the create_volume process altogether.

Currently we seem to have create_export, ensure_export and
now initialize that all are designed to do very similar
things.

A bug has been filed to address this and will attempt
to collapse these functions to be done at attach time.

This particular patch in essence reverts two patches:
commit: 18f8f5be94aae3b1747b143479ea1b188872f000
commit: a9267644ee09591e2d642d6c1204d94a9fdd8c82

Change-Id: Ib615847f3cbeb74b1e4416d51730162ad1d07a40
Closes-Bug: 1270608
Merge "Revert initialize_connection changes"
Merge "VolumeManager: initialize even if a volume can't be found"