Change "secrete" to "secret"

Apparently this is intentional as a joke on devstack leaking
passwords, but the dual meaning of the word confuses people.  Let's
change it before we get yet another review fixing it.

Change-Id: I3bee03612f6ea197362aab04a37f81043f77f235
diff --git a/lib/tempest b/lib/tempest
index 3b8a888..19b63d1 100644
--- a/lib/tempest
+++ b/lib/tempest
@@ -176,7 +176,7 @@
     sudo install -d -o $STACK_USER $TEMPEST_CONFIG_DIR
     rm -f $TEMPEST_CONFIG
 
-    local password=${ADMIN_PASSWORD:-secrete}
+    local password=${ADMIN_PASSWORD:-secret}
 
     # See ``lib/keystone`` where these users and tenants are set up
     local admin_username=${ADMIN_USERNAME:-admin}