Not an SRX expert by any stretch of the imagination but without IRB how are you connecting via SSH to the SRX to start with, is it via FXP0? If yes, then I believe (for sure?) that changing l2-learning global-mode should have no affect on your ability to reach the SRX after the reboot.
2nd if you want to use commit confirmed within a SRX cluster you must be in config exclusive to start with. Otherwise the standby node will rollback even after a commit is entered on the master node. In this situation you would need to perform a cluster conf-sync