cubicweb #3168027 internal sessions only disable integrity hooks until the first commit [validation pending]

because InternalSession.__init__ doesn't handle the transaction's ctx_count, a commit or rollback will free the thread-local data and reset all hooks to enabled. While InternalSession's "unsafe by default" behaviour is questionable, changing behaviour in the middle of the session is terribly counter-intuitive.

prioritynormal
typebug
done in3.17.7
load0.500
load left0.000
closed by#6356adcb652c [server] Make internal sessions not reset 'safe'-ness on first commit
patch[server] Make internal sessions not reset 'safe'-ness on first commit [applied]