tests: fix reported patch tool name in test-mq

Strip any path of the patch executable, which it might return on failure.

tests/test-mq

@@ -512,7 +512,7 b' echo % qpush should fail, local changes'
 hg qpush
 
 echo % apply force, should not discard changes with empty patch
-hg qpush -f
+hg qpush -f 2>&1 | sed 's,^.*/patch,patch,g'
 hg diff --config diff.nodates=True
 hg qdiff --config diff.nodates=True
 hg log -l1 -p

tests/test-mq.out

@@ -492,7 +492,7 b' Patch queue now empty'
 abort: local changes found, refresh first
 % apply force, should not discard changes with empty patch
 applying empty
-/usr/bin/patch: **** Only garbage was found in the patch input.
+patch: **** Only garbage was found in the patch input.
 patch failed, unable to continue (try -v)
 patch empty is empty
 Now at: empty