Fix grabserial for use with (some) USB serial adapters

two commits, one is just cleanups I did while trying to find out why grabserial would only work once per boot with my USB serial adapter.

The second commit is a kludge that seems to work reliably to avoid the reboot. Note that unplugging the USB serial adapter and replugging it did not fix the issue.  I bumped the MINOR_VERSION since the API changed compatibly.