handle stash file names with missing keytab type spec and colon in path

handle stash file names with missing keytab type spec and colon in path

Currently the keytab name resolution code will pass off any name with
no colon to the default keytab type handler, which is the FILE
handler.  It will also check for Windows file names consisting of one
letter followed by a colon, and treat them as FILE specs also.

If a UNIX pathname contains a colon, however, and no type was
explicitly specified, the leading part of the pathname gets treated as
a type name and fails to match anything.  It should instead treat
type-less names starting with "/" as FILE specs also.

Tweak the test suite to use such a name.

Report and patch from Apple.  rdar://problem/6179239

ticket: new

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@20872 dc483132-0cff-0310-8789-dd5450dbe970