ncsid: update_ra_gw: Improve gateway discovery speed

The rdisc6 binary when run in a subshell buffers all of the output
instead of sending each line. This results in a long delay to figure out
the gateway address.

We can fix this by running it through `script`, which removes the
buffering and allows us to nearly instantly update our route.

Tested: Ran on our AMD Rome system and verified that the gateway was
quickly being updated.

Change-Id: I22350d6bd95665ab853c3f1273c0d6e4ff60718e
Signed-off-by: William A. Kennington III <wak@google.com>
1 file changed