Apparently "make -j 4 distcheck" has a race condition when "installing" in

parallel.  Remove the "-j 4" so we don't get random tarball build failures.
Hopefully this won't take all that much longer to make the tarball each night.

This commit was SVN r18552.

contrib/nightly/create_tarball.sh

@@ -285,7 +285,7 @@ do_command "./configure --enable-dist"
 # that this may need to change in the future...
 save=$LD_LIBRARY_PATH
 LD_LIBRARY_PATH=
-do_command "make -j 4 distcheck"
+do_command "make distcheck"
 LD_LIBRARY_PATH=$save
 save=