pull up r20028 from trunk

pull up r20028 from trunk

 r20028@cathode-dark-space:  jaltman | 2007-10-01 01:19:05 -0400
 ticket: new
 subject: NIM: BUG: APP: leaking prompts in obtain new credentials dialog

 The Kerberos v5 plug-in for Network Identity Manager was not clearing
 the list of prompts properly when a user changes the active identity
 in the new credentials dialog.  The stale prompts would be visible to
 the user if the newly selected identity is invalid or the new identity
 cannot be validated.

 This patch clears the prompts if there is an identity change.

ticket: 5793
version_fixed: 1.6.3

git-svn-id: svn://anonsvn.mit.edu/krb5/branches/krb5-1-6@20069 dc483132-0cff-0310-8789-dd5450dbe970