chan_lcr: fixed race condition in new ref assignment

chan_lcr: fixed race condition in new ref assignment

LCR assumes, that any call in the list, that has ref set to 0 is waiting for a ref to be assigned.
That can cause trouble, if we have one call waiting for a ref to be assigned and another call
hanging in the list, that was just released in the same moment.

Both have ref == 0 and in some circumstances, the new ref message picks the wrong one for
assignment...

This patch makes chan_lcr distinguish between calls waiting for a new ref and those, that
only have their ref removed due to release. (It is not enough, to check for state, since
new calls can change into release state immediately! That is also one of the race conditions,
when this can get you into trouble: asterisk receives call1 by LCR, makes a SETUP call2 immediately
through LCR and then receives a release for call1 by LCR before call2 got it's ref assigned!)

This patch also removes some dead code, that was #ifdef'd out.

End user notice: if you ever got into the situation, that _all_ calls from asterisk to LCR got released
immediately and only a restart of asterisk got you out of the situation, then you might need
this fix :)