topicmap: move the monkey patching into a context manager
There is a couple of other place doing branchmap/topicmap update (of the served
set), we'll have to set the monkey patching for them.
This changeset is just doing the move to a context manager to make sure it is
correct.
#!/bin/sh
# This file holds logic that is used in many tests.
# It can be called in a test like this:
# $ . "$TESTDIR/testlib"
# Enable obsolete markers and enable extensions
cat >> $HGRCPATH << EOF
[experimental]
evolution=createmarkers,exchange
[extensions]
rebase=
EOF
echo "topic=$(echo $(dirname $TESTDIR))/src/topic" >> $HGRCPATH