Revert changes made for CA-122205

Roll back fixes that ignore journal unavailability exceptions.
Issue being fixed under CA-129800 by correcting the original changes
made for CP-5818. Commits being reverted are:

* 2171f7d: "CA-122205: More race conditions."
* 4e92794: "CA-122205: Continuation to the previous commits"
* 84dcbf4: "CA-122205: Addressing build errors, also backing out blktap2 changes"
* 68286d1: "CA-122205: Resolve race between VDI.activate and GC."

Signed-off-by: Chandrika Srinivasan <chandrika.srinivasan@citrix.com>
Reviewed-by: Vineeth Thampi Raveendran <vineeth.thampi@citrix.com>

GitHub: closes #96 on xapi-project/sm
CA-129800: Use VDI id in journal names.

Use VDI id (origUuid) in journal file names instead of clone/leaf id.
This makes it possible to detect existence of journal files for a
certain VDI without needing to open and read the files for
additional information.

Signed-off-by: Chandrika Srinivasan <chandrika.srinivasan@citrix.com>
Reviewed-by: Vineeth Thampi Raveendran <vineeth.thampi@citrix.com>

GitHub: closes #98 on xapi-project/sm
CA-114341: explicitly use keyword argument

Signed-off-by: Thanos Makatos <thanos.makatos@citrix.com>
Reviewed-by: Germano Percossi <germano.percossi@citrix.com>
CA-114341: don't try to reacquire the lock

Signed-off-by: Thanos Makatos <thanos.makatos@citrix.com>
Reviewed-by: Germano Percossi <germano.percossi@citrix.com>
Merge CA-114341

Signed-off-by: Germano Percossi <germano.percossi@citrix.com>

Github: closes #97 on xapi-project/sm