Please give-back ns3 on armhf

[Aron Xu <aron@debian.org>]

Dear wb-team,

Please give back ns3 3.17+dfsg-1 on armhf. It failed because of
needing more memory than available, while the build of same version
was successful on armel, I think it still worth trying a second time
before giving up on the architecture.

gb ns3_3.17+dfsg-1 . armhf

Thanks,

Aron