Code review request: 8001208: Fix for KRB5CCNAME not complete

[Weijun Wang]

Please take a look at

    http://cr.openjdk.java.net/~weijun/8001208/webrev.00/

An old test is enhanced to check for the fix.

Honestly, it might be best to check for KRB5CCNAME outside 
FileCredentialsCache since the ccache type can be something other than 
FILE:. It will touch more files and I decide to delay this enhancement 
until we start supporting more real types.

Also, I want to backport this fix to 7u, so it had better be simple.

Thanks
Max