mwan3: update to version 1.5-7

Fixed issue where an manual ifup-ed interface would immediatly go down again
Remove from init as mwan3 is not a service

Signed-off-by: Jeroen Louwes <jeroen.louwes@gmail.com>
Merge pull request #390 from Adze1502/master

mwan3: update to version 1.5-7