vlog: Be more liberal in syntax for -v and vlog/set.

vlog: Be more liberal in syntax for -v and vlog/set.

Until now, the argument to -v and vlog/set has had to take the form
"module:facility:level".  I can never remember the required order, so this
commit switches to allowing any order.

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