daemon: Make --monitor process change its process title.

daemon: Make --monitor process change its process title.

When --monitor is used, administrators sometimes become confused about the
presence of two copies of each process.  This commit attempts to clarify
the situation by making the monitoring process change its process name, as
seen in /proc/$pid/cmdline and in "ps", to clearly indicate what is going
on.

CC: Dan Wendlandt <dan@nicira.com>