LKC-40: Synchronise calls to the same activity and attempt to create a session, if it does not exist. Even though the method creating sessions in LamsCoreToolService is synchronised, subsequent reads from DB are (probably) dirty, i.e. they show that session does not exist while it is already there, created by another, isolated transaction. Reattempting session creation from within transaction not only is broken (because of the dirty reads) but also does not make sense, because if the session already exists, there is no point in repeating a failed attempt to create it. The synchronisation code prevents threads from creating sessions at the same time and even if anything happens, allows an user to carry on.
