gfapi: always close the fd in glfs_h_creat()

When running stress and performance tests against nfs-ganesha, the
number of open file descriptors increases continously. If the tests run
long enough, the brick processes will eventually run out of file
descriptors.

This seems to be caused by glfs_h_creat() which allocates a 'struct
glfs_fd', but does not release it. A normal glfs_creat() returns the
file descriptor to the application, whereas glfs_h_creat() returns a
handle (struct glfs_object). The file descriptor associated with the
handle can not be release by glfapi-applications.

This fd-leak can be prevented by destroying the 'struct glfs_fd' before
returning the 'struct gfls_object' to the gfapi-application.

Change-Id: I32465077a35cd0449a8e584c53899b32f022e5af
BUG: 1176242
Signed-off-by: Niels de Vos <ndevos@redhat.com>
Reviewed-on: http://review.gluster.org/9318
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>
Reviewed-by: Shyamsundar Ranganathan <srangana@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>