storage/posix: do not dereference gfid symlinks before posix_handle_mkdir_hashes()

Whenever a new directory is created, its corresponding gfid file must
also be created. This was done first calling MAKE_HANDLE_PATH() to get
the path of the gfid file, then calling posix_handle_mkdir_hashes() to
create the parent directories of the gfid, and finally creating the
soft-link.

In normal circumstances, the gfid we want to create won't exist and
MAKE_HANDLE_PATH() will return a simple path to the new gfid. However if
the volume is damaged and a self-heal is running, it is possible that we
try to create an already existing gfid. In this case, MAKE_HANDLE_PATH()
will return a path to the directory instead of the path to the gfid.

To solve this problem, every time a path to a gfid is needed, a call to
MAKE_HANDLE_ABSPATH() is made instead of the call to MAKE_HANDLE_PATH().

BUG: 1099955
Change-Id: I5bcd2b3c38d172c75946f33519e057e76d960a24
Signed-off-by: Xavier Hernandez <xhernandez@datalab.es>
Reviewed-on: http://review.gluster.org/6737
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>