test: use bundle2 for exchange in test-largefile
Using bundle2 for exchange unlock the usage of changegroup version 2. This
version of the changegroup held more information (delta base) that result in a
small increase in content size.
It also lead to reordering of output because the exchange scheduling is a bit
different.
fixbundle() {
grep -v 'saving bundle' | grep -v 'saved backup' | \
grep -v added | grep -v adding | \
grep -v "unable to find 'e' for patching" | \
grep -v "e: No such file or directory"
}