glusterd: Use mkdir_p to create DEFAULT_WORKDIR

On non-Linux platforms FSH(Filesystem Hierarchy Standard)
is not followed 'create' the default expected directory.

Change-Id: Ia55dc99aa398efb6d2d140985cbc0ae11bdc763c
BUG: 1111774
Signed-off-by: Harshavardhana <harsha@harshavardhana.net>
Reviewed-on: http://review.gluster.org/8155
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Prashanth Pai <ppai@redhat.com>
Reviewed-by: Humble Devassy Chirammal <humble.devassy@gmail.com>