oeqa/runtime/systemd: remove race in settle()

The settle() function had a race where services could still be activating at two
minutes but then when the final log is output, they've activated.

Remove this race and generally clean up the code.

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>