Create 32 chars passwords by default

this will play nicer with our defaults when security compliance is
enabled in Keystone and allow us to use dynamic credentials in tempest.

Change-Id: Ifec79fdb854b529819a4eecd43c442298ac5e442
Related-Issue: PROD-29305
diff --git a/tempest/lib/common/utils/data_utils.py b/tempest/lib/common/utils/data_utils.py
index c5df590..8daffe9 100644
--- a/tempest/lib/common/utils/data_utils.py
+++ b/tempest/lib/common/utils/data_utils.py
@@ -59,7 +59,7 @@
     return rand_name
 
 
-def rand_password(length=15):
+def rand_password(length=32):
     """Generate a random password
 
     :param int length: The length of password that you expect to set