Changes

testenv: allow -c osmo-hlr -> testenv_osmo_hlr.cfg

For the HLR testsuite, we now have testenv_pyhss.cfg and
testenv_osmo_hlr.cfg. The parameters to select the config are "-c pyhss"
and "-c osmo_hlr", derived from these filenames. However "-c osmo-hlr"
is more intuitive and I keep writing that. Replace - with _
automatically to make this more intuitive.

Change-Id: Ib9e7083799d236ec30a378a08552be3d1a5a4aba