[SCSI] libfc: when rport goes away (re-plogi), clean up exchanges to/from rport

When a rport goes away, libFC does a plogi which will reset exchanges
    at the rport. Clean exchanges at our end, both in transport and libFC.
    If transport hooks into exch_mgr_reset, it will call back into
    fc_exch_mgr_reset() to clean up libFC exchanges.

Signed-off-by: Abhijeet Joglekar <abjoglek@cisco.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>