MB-7930: delete all but 10 last erl_crash.dump-s

Change-Id: Iab52965c8a04a41f4d661529d434191aaa2cde8a
Reviewed-on: http://review.couchbase.org/27682
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>