Dendrite tests failing on `develop`

[clokep]

Looks decent enough to me. Dendrite is likely unhappy because you're now relying on device lists in /sync which Dendrite has issues with.

@kegsay is it worth blacklisting these in Dendrite? (On the one hand I didn't want to suppress the fact that dendrite has an issue there; on the other I don't want to cause people pain by having CI failures across the board.)

Originally posted by @DMRobertson in #1142 (comment)

[clokep]

@kegsay / @neilalexander Any thoughts on what we should do here? Should we blacklist those tests for Dendrite for now?

[neilalexander]

Yes, I think that probably makes sense for now. We do have known issues with device list syncing.