afr: Modified book-keeping structures for entrylks

* There are upto 3 entry lockees that may be needed to perform
  entrylk'ing in posix dir-write operations.

* For eg, rmdir ("/a/b") needs to acquire locks on two entities,
  - entrylk ("/a", "b")
  - entrylk ("/a/b", null)

* Changed existing entrylk/rename/selfheal (entrylk) transactions
  to use the new book-keeping structures

* Fixed few issues in afr_trace_entry_lk{in,out} functions. Tracing is now
  aware of the new entry lockee structure.

Implementation notes:
* Changed 'cookie' sent in stack_wind to encode lockee_entity_no
  and subvol_no.

  cookie is a non-negative integer such that 0 <= cookie < replica_count,
  When more than one lock is being acquired across the subvolumes,
  cookie % replica_count gives the subvol_no
  cookie / replica_count gives the lockee_entity_no.

Change-Id: Idbf41803387a7d59a0f7fcb1453d91cea74da153
BUG: 765564
Signed-off-by: Krishnan Parthasarathi <kp@gluster.com>
Reviewed-on: http://review.gluster.org/2828
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>