ptserver: Fix parallel builds

ptserver: Fix parallel builds

It's not safe to have libtool building a blah.lo at the same time as
gcc is building blah.o. A Makefile must exclusively use either the .lo
or the .o form.

Fix ptserver so that ptint.xdr.lo is the only one referenced, and just
explicitly pull in the LWP object for the ptserver.

Change-Id: I2e868d2d318c84e20bcccc0ffc462c87e4b7a2f2
Reviewed-on: http://gerrit.openafs.org/8100
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>