afsd: afsd.fuse needs MT_LIBS

This fixes a build failure on Ubuntu raring as of binutils
2.23.1-0ubuntu8, which pulled in a bugfix that makes
--no-copy-dt-needed-entries stricter:
http://sourceware.org/git/?p=binutils.git;a=commit;h=63f3bee644cc30f1e6d049ca54d307a7c63b8186

make[3]: Entering directory `/…/src/afsd'
gcc  -O -I/…/src/config -I/…/include -I. -I.  -D_LARGEFILE64_SOURCE   -I/…/src/afs -I/…/src/afs/UKERNEL -I/…/src/rx/UKERNEL -DUKERNEL -D_FILE_OFFSET_BITS=64 -I/usr/include/fuse   -o afsd.fuse afsd_fuse.o     /…/lib/libuafs.a /…/lib/libdes.a /…/lib/libafsutil.a /…/lib/libcmd.a /…/lib/libafsutil.a -lresolv   -lfuse
/usr/bin/ld.bfd.real: /…/lib/libuafs.a(afs_usrops.o): undefined reference to symbol 'pthread_setspecific@GLIBC_2.2.5'
/usr/bin/ld.bfd.real: note: 'pthread_setspecific@GLIBC_2.2.5' is defined in DSO /lib/x86_64-linux-gnu/libpthread.so.0 so try adding it to the linker command line
/lib/x86_64-linux-gnu/libpthread.so.0: could not read symbols: Invalid operation
collect2: error: ld returned 1 exit status
make[3]: *** [afsd.fuse] Error 1
make[3]: Leaving directory `/…/src/afsd'

This is roughly a partial cherry-pick of commit
f6d7a4b426f55db366113bbdda4da71570310410 (which doesn’t apply on
1.6.x), although this particular build failure had already been fixed
on master as a side effect of commit
98f86cfc53fc987fdaed2f5bb733b5b5d21bfda9.

Change-Id: I89467f00bbf511ec63c464b656d342c5fd2ce557
Signed-off-by: Anders Kaseorg <andersk@mit.edu>
Reviewed-on: http://gerrit.openafs.org/9387
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Tested-by: Stephan Wiesand <stephan.wiesand@desy.de>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>