MB-100: exit testrunner if ini file is not found

Change-Id: I046357b2dfc04af9a5a2bb691e5ee305ec8c8a48
Reviewed-on: http://review.couchbase.org/23778
Reviewed-by: Pavel Paulau <pavel.paulau@gmail.com>
Tested-by: buildbot <build@couchbase.com>