rpm: move the mount/api xlator to the glusterfs-api sub-package

The main glusterfs package included the xlator/api.so file which caused
a dependency on the glusterfs-api package:

  # rpm -i glusterfs-3.4.0-0.6.beta3.el6.x86_64.rpm
  error: Failed dependencies:
  libgfapi.so.0()(64bit) is needed by glusterfs-3.4.0-0.6.beta3.el6.x86_64

Moving the mount/api xlator to the glusterfs-api package will prevent
the automatic dependency generator to add the dependency to the main
package.

Change-Id: I4650c40cdfe610b9b69bab07d262093854aa6583
BUG: 950083
Reported-by: Vijay Bellur <vbellur@redhat.com>
Signed-off-by: Niels de Vos <ndevos@redhat.com>
Reviewed-on: http://review.gluster.org/5255
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>