Recapture screen service logs; disable sysloging.

Using syslog as the single point of OpenStack service data when running
devstack-gate is clunky. Exception tracebacks are compressed into a
single line making it hard to read what broke. Return to capturing
individual screen logs, but don't duplicate those logs to syslog
anymore.

Change-Id: I17e31b4ffde00bb57f70129710c1b6bb1584a5fa
Merge "Recapture screen service logs; disable sysloging."