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
revert CA-114341 patches

The CA-114341 patches fail to pass the BST as some curious locking
issues appear. It's not yet clear whether these patches are just wrong
or whether they uncover an existing issue. I'm removing them for now to
unblock the BST and the merge into trunk.

This patch reverts the following commits:
* 8c1c069c: "CA-114341: don't try to reacquire the lock"
* 1f5db2b3: "CA-114341: explicitly use keyword argument"
* a47ceebb: "CA-114341: GC: acquire VDI lock non-blocking"

Signed-off-by: Thanos Makatos <thanos.makatos@citrix.com>