Do not modify rsyslog files if rsyslog is not used.

Swift was missing an 'if [[ $SYSLOG != "False" ]]' statement which is used
by other services, and therefor failed with a 'No such file or directory'
error when 'SYSLOG=False' was set in localrc.

Closes-Bug: 1308461

Change-Id: I8655a955ebb322516d92bee418b93d4cc23bdc5c
Merge "Do not modify rsyslog files if rsyslog is not used."