mq: really remove undo after a qpush (and after a strip)
For qpush, removeundo has to be called after the transaction has finished.
strip may use unbundle, which also leaves an undo file.
Fixes issue780.
#!/bin/sh
hg init
echo This is file a1 > a
hg add a
hg commit -m "commit #0" -d "1000000 0"
ls
echo This is file b1 > b
hg add b
hg commit -m "commit #1" -d "1000000 0"
hg co 0
# B should disappear
ls