netdev-linux: Skip miimon execution when disabled

When dealing with a large number of ports, one of the performance
bottlenecks is that we loop through all netdevs in the main loop. Miimon
is a contributor to this, checking all devices even if it has never been
enabled.

This patch introduces a counter for the number of netdevs with miimon
configured. If this is 0, then we skip miimon_run() and miimon_wait().
In a test environment of 5000 internal ports and 50 tunnel ports with
bfd, this reduces CPU usage from about 50% to about 45%.

Signed-off-by: Joe Stringer <joestringer@nicira.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>
ovs-controller: Rename test-controller and do not install or package.

Too many users have incorrectly assumed that ovs-controller is a necessary
or desirable part of an Open vSwitch deployment.  This commit should fix
the problem by renaming it test-controller and removing it from the
default install and from packaging.

Signed-off-by: Ben Pfaff <blp@nicira.com>
daemon: Precisely document signals that cause the monitor to restart.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Joe Stringer <joestringer@nicira.com>