bundle: do no check the changegroup version if no changegroup is included
We don't need to check the compatibility of something we will not use.
In practice this was getting in the was of `streamv2` bundles on a narrow
repository as the 'cg.version=02' value was rejected by this checks.
#require bzr
$ . "$TESTDIR/bzr-definitions"
$ cat > treeset.py <<EOF
> import sys
> from breezy import workingtree
> import breezy.bzr.bzrdir
> wt = workingtree.WorkingTree.open('.')
>
> message, rootid = sys.argv[1:]
> wt.set_root_id(b'tree_root-%s' % rootid.encode())
> wt.commit(message)
> EOF
change the id of the tree root
$ mkdir test-change-treeroot-id
$ cd test-change-treeroot-id
$ brz init -q source
$ cd source
$ echo content > file
$ brz add -q file
$ brz commit -q -m 'Initial add'
$ "$PYTHON" ../../treeset.py 'Changed root' new
$ cd ..
$ hg convert source source-hg
initializing destination source-hg repository
scanning source...
sorting...
converting...
1 Initial add
0 Changed root
$ manifest source-hg tip
% manifest of tip
644 file
$ cd ..