salt: Switch to ni/skyline-18.1/2017.7 branch
salt: Switch to ni/skyline-18.1/2017.7 branch

Signed-off-by: Ovidiu-Adrian Vancea <5c8543b42e0c702ca83e838bf20f72a81672f5ef@ni.com>

ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt