Don't pass password to innobackup via command line, use environment instead

Signed-off-by: Julius Goryavsky <julius.goryavsky@mariadb.com>

scripts/wsrep_sst_mariabackup.sh

@@ -868,10 +868,10 @@ then
         fi
 
         if [ -n "${WSREP_SST_OPT_PSWD:-}" ]; then
-           INNOEXTRA+=" --password=$WSREP_SST_OPT_PSWD"
+            export MYSQL_PWD=$WSREP_SST_OPT_PSWD
         elif [[ $usrst -eq 1 ]];then
-           # Empty password, used for testing, debugging etc.
-           INNOEXTRA+=" --password="
+            # Empty password, used for testing, debugging etc.
+            unset MYSQL_PWD
         fi
 
         get_keys

scripts/wsrep_sst_xtrabackup-v2.sh

@@ -958,10 +958,10 @@ then
         fi
 
         if [ -n "${WSREP_SST_OPT_PSWD:-}" ]; then
-           INNOEXTRA+=" --password=$WSREP_SST_OPT_PSWD"
+            export MYSQL_PWD=$WSREP_SST_OPT_PSWD
         elif [[ $usrst -eq 1 ]];then
-           # Empty password, used for testing, debugging etc.
-           INNOEXTRA+=" --password="
+            # Empty password, used for testing, debugging etc.
+            unset MYSQL_PWD
         fi
 
         get_keys