Crypto: Threading: Do things on right thread (2/X)
Crypto: Threading: Do things on right thread (2/X)

Encryption is now totally threaded.
Fix calls of mxsession.matrixClient.

matrix-org/matrix-ios-sdk,matrix-org/matrix-ios-sdk,matrix-org/matrix-ios-sdk,matrix-org/matrix-ios-sdk,matrix-org/matrix-ios-sdk