glupy: build fix if python and glusterfs prefix differ

If python is installed in ${pythonprefix} and glusterfs
in ${glusterfsprefix}, we have the following values:
${PYTHON}-config --prefix   => ${pythonprefix}
$libdir                     => ${glusterfsprefix}/lib

Using LDFLAGS="-L`${PYTHON}-config --prefix`/$libdir" we lookf for
python libraries in ${pythonprefix}/${glusterfsprefix}/lib while
we should be looking for ${pythonprefix}/lib

Replacing $libdir by lib breaks bug 1159248, so let us look in both
${pythonprefix}/lib and ${pythonprefix}/$libdir

Backport of: I2fef1b795235d1543a0e5ac619c6c2d59127fb66

BUG: 1138897
Change-Id: I29b9f121e1cdc546ca8551ff48cc99f1c71a0ea6
Signed-off-by: Emmanuel Dreyfus <manu@netbsd.org>
Reviewed-on: http://review.gluster.org/9214
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Reviewed-by: Raghavendra Bhat <raghavendra@redhat.com>
Tested-by: Raghavendra Bhat <raghavendra@redhat.com>