hghave: disable demandimport when chg is running
Chg disables demandimport on purpose for performance wins and
therefore, it probably makes sense to indicate that demandimport is disabled
when chg is running.
Test Plan:
Ran all the tests.
Differential Revision: https://phab.mercurial-scm.org/D1161
#require serve killdaemons
$ hg clone http://localhost:$HGPORT/ copy
abort: * (glob)
[255]
$ test -d copy
[1]
$ $PYTHON "$TESTDIR/dumbhttp.py" -p $HGPORT --pid dumb.pid
$ cat dumb.pid >> $DAEMON_PIDS
$ hg clone http://localhost:$HGPORT/foo copy2
abort: HTTP Error 404: * (glob)
[255]
$ killdaemons.py