Bump send MMS timeout, Use cell data for MMS

The `test_sms_with_attachment` is a bit unreliable. There seem to be some differences in the performance and ability of SIMs to send MMS.

With this I'm trying to find a better middle ground (using cell data) and increasing the timeout to cope with regional differences.

We must run this through `ad_hoc` job several times on both master and v1-train.

`master` -> yes
`v1-train` -> yes