gluster: Fix vdsm gluster api schema error

fixed typo and renamed 'boolean' into 'bool' in json schema file
and renamed 'type' into 'mimetype'.

Change-Id: I1f54251a99bff1a16d6bc2a3e692855dab6c8561
Signed-off-by: Timothy Asir <tjeyasin@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/15331
Reviewed-by: Aravinda VK <avishwan@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>