vlib dhcp: default to logging without elogs

Some components, like dhcp, log constantly changing strings which in
turn forces elog string table to grow unbound.

To avoid this, as a workaround, only turn on elog logging if requested.
Actual fix that adds configuration for logging subclasses should come in
a later patch.

Type: improvement

Signed-off-by: Florin Coras <fcoras@cisco.com>
Change-Id: Ie8b26251fb7115d866c2bd65353daa33cdab1ab6

src/vlib/log.c

@@ -25,7 +25,7 @@ vlib_log_main_t log_main = {
   .default_syslog_log_level = VLIB_LOG_LEVEL_WARNING,
   .unthrottle_time = 3,
   .size = 512,
-  .add_to_elog = 1,
+  .add_to_elog = 0,
   .default_rate_limit = 50,
 };