Modify default logging of SIP2 in oils_ctl.sh.

Change the default of OILS_SIP_ERR_LOG from /dev/null to
LOCALSTATEDIR/log/oils_sip.log to mirror what is done with the
Z39.50 log.

Signed-off-by: Jason Stephenson <jstephenson@mvlc.org>
Signed-off-by: Ben Shum <bshum@biblio.org>