pull up r19400 from trunk

pull up r19400 from trunk

 r19400@cathode-dark-space:  lxs | 2007-04-05 16:33:40 -0400
 ticket: new
 subject: krb5int_open_plugin_dirs errors out if directory does not exist

 If one of the directories in the list doesn't exist and no filenames are
 passed in because opendir fails and then the code gets an error.  opendir()
 failing should not be a fatal error.  The function should just move on to
 the next directory.

ticket: 5510
version_fixed: 1.6.1

git-svn-id: svn://anonsvn.mit.edu/krb5/branches/krb5-1-6@19417 dc483132-0cff-0310-8789-dd5450dbe970