cluster/afr: Fix all locked_on bricks are sinks check in self-heals

        Backport of http://review.gluster.org/8456

Problem:
Counts may give wrong results when the number of bricks is > 2. If the
locks are acquired on one source and sink, but the source accuses even the
down sink then there will be 2 sinks and lock is acquired on 2 bricks so
even when there is a clear source and sink **_finalize_source functions think
the file/directory is in split-brain.

Fix:
Check that all the bricks which are locked are sinks.

BUG: 1136829
Change-Id: I56a8f9ff261bdeec8c441237c485036141b6f00d
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/8593
Reviewed-by: Krutika Dhananjay <kdhananj@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Ravishankar N <ravishankar@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
storage/posix: Prefer gfid links for inode-handle

        Backport of http://review.gluster.org/8575

Problem:
File path could change by other entry operations in-flight so if renames are in
progress at the time of other operations like open, it may lead to failures.
We observed that this issue can also happen while renames and readdirps/lookups
are in progress because dentry-table is going stale sometimes.

Fix:
Prefer gfid-handles over paths for files. For directory handles prefering
gfid-handles hits performance issues because it needs to resolve paths
traversing up the symlinks.
Tests which test if files are opened should check on gfid path after this change.
So changed couple of tests to reflect the same.

Note:
This patch doesn't fix the issue for directories. I think a complete fix is to
come up with an entry operation serialization xlator. Until then lets live with
this.

BUG: 1136821
Change-Id: If93e46d542a4e96a81a0639b5210330f7dbe8be0
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/8594
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>