ovs-bugtool: Provide a separate capability to openvswitch logs.

ovs-bugtool: Provide a separate capability to openvswitch logs.

Currently we have a 50 MB size limitation for all logs. This looks
quite less because a single uncompressed log can be 50 MB which
will result in ovs-bugtool picking a single log.

While debugging issues related to openvswitch, it is important that
we have all logs related to openvswitch atleast. This patch provides
a new capability for openvswitch logs with no size limitation. This
should not be a problem since compression reduces the size of the logs
quite a bit.

Also increase the size limitation for the regular system logs to 200 MB.

A future commit adds an option '--log-days' to control the number of logs
that we collect.

Signed-off-by: Gurucharan Shetty <gshetty@nicira.com>