mail: allow jkrauska to read logs

As per RT #8214, Joel needs to read mail logs for
troubleshooting. Allowing his group (of one!) sudo rights as the syslog
user will allow him just that.

Change-Id: I3a1c7ce9f12d0751ddc711ca9672e264a8684016
Signed-off-by: Giuseppe Lavagetto <glavagetto@wikimedia.org>