talloc: Use libraries from build dir for testsuite

talloc: Use libraries from build dir for testsuite

There was a failure when tests were executed after after extracting
talloc tarball.

  sh$ make -j8 check
  WAF_MAKE=1 PATH=buildtools/bin:../../buildtools/bin:$PATH waf test
  bin/talloc_testsuite: error while loading shared libraries: libtalloc.so.2: cannot open shared object file: No such file or directory
  sh: ./lib/talloc/test_magic_differs.sh: No such file or directory
  Traceback (most recent call last):
    File "test_pytalloc.py", line 11, in <module>
      import talloc
  ImportError: libtalloc.so.2: cannot open shared object file: No such file or directory

Signed-off-by: Lukas Slebodnik <lslebodn@redhat.com>
Reviewed-by: Andrew Bartlet <abartlet@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>