MB-9472:[couchbase-server] calm ls if erl_crash_dump.* is missing

Change-Id: I1e06ca5f814ca3476ed6b7789c544a99cb8422e0
Reviewed-on: http://review.couchbase.org/30222
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>