python: Do not include time stamp in syslog messages.

python: Do not include time stamp in syslog messages.

vlog.py currently generates the same log messages, starts with the time stamp
information, for console, syslog and file. All messages start with current
time stamp information.

Syslogd, by default, prepends time stamp with each message already. Thus
the time stamp generated by vlog.py is redundant.

This patch removes time stamp from the message before vlog.py sends it
to syslogd.

Signed-off-by: Andy Zhou <azhou@nicira.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>