CMK-38006: ignore redis crashes not naming redis

test-qa-performance-k8s fails on redis crash reports the filter lets
through, e.g. "max number of clients reached." -- the same flake, but
the message does not name redis.

Attribute the exception via its traceback instead. This drops the
"reading from socket" pattern, which matched with no redis reference at
all; that message only comes from redis/_parsers, so the traceback
check covers it.

Continues CMK-38099.

Change-Id: If12c1d2103d9e4b65181eaad44daec9f2574977a