Rseq redirection fails to raise kernel xfer event

#2350 (closed) added rseq support to DR using a run-twice scheme documented in the wiki. On the native run, we can have the kernel abort and target the abort handler for a migration or context switch, with a resulting control flow redirection in the code stream seen by a client. However, DR does not raise a kernel xfer event there. This issue covers adding the event (and probably a new type of transfer).