Fix gprecoverseg that contains bad backport code

The option differentialResynchronization is not defined in the options,
which will cause gprecoverseg fails.

if self.__options.differentialResynchronization:
    self.logger.error("gprecoverseg differential recovery failed. Please check the gpsegrecovery.py log"
                      " file and rsync log file for more details.")
else:
    self.logger.error("gprecoverseg failed. Please check the output for more details.")

Because the code block is miss backported from GPDB upstream.
The code was added in commit 07c4d13

The upstream
greenplum-db/gpdb-archive@b84f08e2e1a299ded905921
introduced this option

Author: gfphoenix78

gpMgmt/bin/gppylib/programs/clsRecoverSegment.py

@@ -378,11 +378,6 @@ def signal_handler(sig, frame):
             if not mirrorBuilder.recover_mirrors(gpEnv, gpArray):
                 if self.termination_requested:
                     self.logger.error("gprecoverseg process was interrupted by the user.")
-                if self.__options.differentialResynchronization:
-                    self.logger.error("gprecoverseg differential recovery failed. Please check the gpsegrecovery.py log"
-                                      " file and rsync log file for more details.")
-                else:
-                    self.logger.error("gprecoverseg failed. Please check the output for more details.")
                 sys.exit(1)
 
             if self.termination_requested: