Save interactive passwords to separate file

The interactive password prompt currently saves to .localrc.auto

However, this is removed when you re-run stack; that is required as it
is how we source the localrc bits of local.conf, and we want the
users' changes to be picked up.

The passwords, however, should remain constant, because everything has
already been setup with them.  So write them to a separate file.  Note
we source before localrc so it can still overwrite them.

Some minor flow-changes too

Change-Id: I9871c8b8c7569626faf552628de69b811ba4dac0
Closes-Bug: #1505872
diff --git a/clean.sh b/clean.sh
index b22a29c..ae28aa9 100755
--- a/clean.sh
+++ b/clean.sh
@@ -134,7 +134,9 @@
 
 # Clean up files
 
-FILES_TO_CLEAN=".localrc.auto docs/files docs/html shocco/ stack-screenrc test*.conf* test.ini*"
+FILES_TO_CLEAN=".localrc.auto .localrc.password "
+FILES_TO_CLEAN+="docs/files docs/html shocco/ "
+FILES_TO_CLEAN+="stack-screenrc test*.conf* test.ini* "
 FILES_TO_CLEAN+=".stackenv .prereqs"
 
 for file in $FILES_TO_CLEAN; do