MDEV-10853 netcat help output in error log when running xtrabackup SST

scripts/wsrep_sst_xtrabackup-v2.sh

@@ -175,7 +175,7 @@ get_transfer()
         fi
         wsrep_log_info "Using netcat as streamer"
         if [[ "$WSREP_SST_OPT_ROLE"  == "joiner" ]];then
-            if nc -h | grep -q ncat;then 
+            if nc -h 2>&1 | grep -q ncat;then 
                 tcmd="nc -l ${TSST_PORT}"
             else 
                 tcmd="nc -dl ${TSST_PORT}"

scripts/wsrep_sst_xtrabackup.sh

@@ -149,7 +149,7 @@ get_transfer()
         fi
         wsrep_log_info "Using netcat as streamer"
         if [[ "$WSREP_SST_OPT_ROLE"  == "joiner" ]];then
-            if nc -h | grep -q ncat;then 
+            if nc -h 2>&1 | grep -q ncat;then 
                 tcmd="nc -l ${TSST_PORT}"
             else 
                 tcmd="nc -dl ${TSST_PORT}"