eccc167 introduced closeHandle which opened the handle,
but never closed it.
Windows handles should be closed.
Updates #921
Signed-off-by: Alex Brainman <alex.brainman@gmail.com>
Due to a copy/paste-o, we were monitoring address changes twice, and
not monitoring route changes at all.
Verified with 'tailscale debug --monitor' that this actually works now (while
running 'route add 10.3.0.0 mask 255.255.0.0 10.0.0.1' and 'route delete (same)'
back and forth in cmd.exe)
In practice route changes are accompanied by address changes and this
doesn't fix any known issues. I just noticed this while reading this
code again. But at least the code does what it was trying to do now.
