webadmin: gluster services - NFS and SHD only

As there are some new service types are added to the enum,
which are not yet implemented in the UI. So adding only
NFS and SHD to the service type drop down.

Change-Id: Icf86977d542e9a31996b94ea8a85c708a6de14e1
Signed-off-by: Kanagaraj M <kmayilsa@redhat.com>