[7u8] Request for approval for CR 7152121 - Krb5LoginModule no longer handles keyTabNames with "file:" prefix

[Weijun Wang]

Hi All

This is a request to backport a jdk8 fix into jdk7u8.

7152121 - Krb5LoginModule no longer handles keyTabNames with "file:" prefix

    http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7152121

The fix is already included in jdk8 as:

    http://hg.openjdk.java.net/jdk8/tl/jdk/rev/61ddc8ce7f3b
    Reviewed-by: mullan

The fix for 7u8 is identical to that of jdk8.

The fix is low-risk, and isolated. new regression test added. Existing 
tests also run fine.

Thanks
Weijun