bundle2: read the whole bundle from stream on abort
When the bundle processing abort on unknown mandatory parts, we now makes sure
all the bundle content is read. This avoid leaving the communication channel in
an unrecoverable state.
$ hg init
$ touch unknown
$ touch a
$ hg add a
$ hg ci -m "1"
$ touch b
$ hg add b
$ hg ci -m "2"
Should show unknown
$ hg status
? unknown
$ hg revert -r 0 --all
removing b
Should show unknown and b removed
$ hg status
R b
? unknown
Should show a and unknown
$ ls
a
unknown