[server] use encryption_key for couchbase env as hash is reserved keyword

scripts/couchbase-test.sh

@@ -36,6 +36,4 @@ if [ "$TYPE" = "WORKER" ]; then
   else
     couchbase-cli server-add --cluster=$COUCHBASE_MASTER:8091 --user=Administrator --password=password --server-add=$IP --server-add-username=Administrator --server-add-password=password
   fi;
-fi;
-
-fg 1
+fi;