mq: use an unfiltered property cache for the queue object
The same `queue` object should be used in all situations. This allows to store
global states on the object (like the reworked shelve extension plans to). The
queue object does not need to be distinct for all possible views (no reference
to the repo/view used at creation time) it's even a bit surprising that mq still
works with the current code.
$ hg init
$ echo 123 > a
$ hg add a
$ hg commit -m "first" a
$ mkdir sub
$ echo 321 > sub/b
$ hg add sub/b
$ hg commit -m "second" sub/b
$ cat sub/b
321
$ hg co 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ cat sub/b 2>/dev/null || echo "sub/b not present"
sub/b not present
$ test -d sub || echo "sub not present"
sub not present