[INTERNAL] removed redundant activity checks

The activity handler should be responsible for activity *sending*.

Removed some checks that were using isInProjectNegotation. Using this
method was more than error prone because there is a short time slice
where users are in the session but not yet in a project negotiation.


Change-Id: Icd6b14cf6cdbb5353bf1929ce4fa0ca94e7e1123
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1410
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>