re-verifying device after device keys have been rotated doesn't mark it as trusted again

[bwindels]

log in with alice
log in with bob and keep open (session 1)
in another browser contect, log in with bob again (session 2)
for bob2, we remove the olm account in idb (key "-"" in account object store)
we reload, this will rotate the keys (log this)
we cross sign bob2 from bob1

expected: bob1 and alice trust bob2 again
observed: bob1 and alice don't trust bob2 again

[jryans]

Seems like a good thing to track, but probably it can wait until after cross-signing release.