Updated configuration and docs for MYSQL_PASSWORD

Updated MYSQL_PASSWORD to DATABASE_PASSWORD in sample
configuration and existing docs

Change-Id: Iafb295a0b7707e08a81e6528620db8543d40f7ae
diff --git a/doc/source/guides/multinode-lab.rst b/doc/source/guides/multinode-lab.rst
index 1530a84..5660bc5 100644
--- a/doc/source/guides/multinode-lab.rst
+++ b/doc/source/guides/multinode-lab.rst
@@ -128,7 +128,7 @@
     MULTI_HOST=1
     LOGFILE=/opt/stack/logs/stack.sh.log
     ADMIN_PASSWORD=labstack
-    MYSQL_PASSWORD=supersecret
+    DATABASE_PASSWORD=supersecret
     RABBIT_PASSWORD=supersecrete
     SERVICE_PASSWORD=supersecrete
     SERVICE_TOKEN=xyzpdqlazydog
@@ -169,7 +169,7 @@
     MULTI_HOST=1
     LOGFILE=/opt/stack/logs/stack.sh.log
     ADMIN_PASSWORD=labstack
-    MYSQL_PASSWORD=supersecret
+    DATABASE_PASSWORD=supersecret
     RABBIT_PASSWORD=supersecrete
     SERVICE_PASSWORD=supersecrete
     SERVICE_TOKEN=xyzpdqlazydog