Fix default gateway IP address parsing

Use route table flags to parse (G)ateway which is (U)p
Fixes cases when there is multiple 'default' named routes

Open-webOS-DCO-1.0-Signed-off-by: Janne Kiiski <janne.kiiski@palm.com>

Change-Id: I5e2deb6bcd100941129a968e82c7d70241f9d65b
Reviewed-on: https://g2g.palm.com/1640
Reviewed-by: Build Verification
Reviewed-by: Janne Kiiski <janne.kiiski@palm.com>
Tested-by: Janne Kiiski <janne.kiiski@palm.com>
Reviewed-by: Keith Derrick <keith.derrick@lge.com>