Synced xtrabackup SST fixes from Percona tree (as of PXC 5.6.24-25.11 release). This fixes/adresses the following LP bugs:

- LP1380697: wsrep_sst_xtrabackup-v2 doesn't stop when mysql is SIGKILLed. (full fix for this (as engineeered by Percona) requires Linux-specific patch that we don't carry, but keep xtrabackup scripts as close as possible)
  - LP1399134: Log the innobackupex/SST logs in SST to syslog if possible. (fixed)
  - LP1405668: Race condition between donor and joiner in PXB SST. (fixed)
  - LP1405985: Fail early if xtrabackup_checkkpoints is missing. (fixed)
  - LP1407599: wsrep_sst_xtrabackup-v2 script causes innobackupex to print a false positive stack trace into the log. (fixed)
  - LP1441762: IST Fails with SST script error. (fixed)
  - LP1451670: Fail when move-back fails in xtrabackup SST. (fixed)

scripts/wsrep_sst_xtrabackup.sh

@@ -149,7 +149,11 @@ get_transfer()
         fi
         wsrep_log_info "Using netcat as streamer"
         if [[ "$WSREP_SST_OPT_ROLE"  == "joiner" ]];then
-            tcmd="nc -dl ${TSST_PORT}"
+            if nc -h | grep -q ncat;then 
+                tcmd="nc -l ${TSST_PORT}"
+            else 
+                tcmd="nc -dl ${TSST_PORT}"
+            fi
         else
             tcmd="nc ${REMOTEIP} ${TSST_PORT}"
         fi