race-condition in isIdUsed

[kitsudaiki]

the method isIdUsed in the session-handler has a race-condition. IDs of sessions in the pending list, are ignored and even, if they are not ignored, there is a little time-window, where IDs are used, but in no list.

This race-condition must be avoided, to avoid double usage of IDs.

The current ignorance of the pending IDs is the reasion, why the test actually works. More correctly, only two differenc instances of the test-binary should be able to create a session.

[kitsudaiki]

will change the init process so that both sides of a session can have different ids. Instead of this both side have to save the id of the other side. This makes many things easier.

[kitsudaiki]

will be resolved with #15