bundle2: fix broken compression engine assertion
bundletype() is a function, so it needs to be called, and it is
documented to return a 2-tuple. This code is untested, so that's why
we haven't noticed the bad assertion.
Differential Revision: https://phab.mercurial-scm.org/D5155
https://bz.mercurial-scm.org/1089
$ hg init
$ mkdir a
$ echo a > a/b
$ hg ci -Am m
adding a/b
$ hg rm a
removing a/b
$ hg ci -m m a
$ mkdir a b
$ echo a > a/b
$ hg ci -Am m
adding a/b
$ hg rm a
removing a/b
$ cd b
Relative delete:
$ hg ci -m m ../a
$ cd ..