[krbdev.mit.edu #8895] ksu broken on 1.18

[Garrett Wollman via RT]

Sun Apr 05 23:42:38 2020: Request 8895 was acted upon.
 Transaction: Ticket created by wollman at bimajority.org
       Queue: krb5
     Subject: ksu broken on 1.18
       Owner: Nobody
  Requestors: wollman at bimajority.org
      Status: new
 Ticket <URL: https://krbdev.mit.edu/rt/Ticket/Display.html?id=8895 >


The change described thusly in the release notes:

	setuid programs will automatically ignore environment
	variables that normally affect krb5 API functions, even if the
	caller does not use krb5_init_secure_context().

breaks ksu when run in an ssh session (either interactively, or, e.g.,
by ansible).  ssh creates separate ccaches for each session and sets
KRB5CCNAME accordingly; ignoring the process environment causes ksu to
look at the nonexistent default ccache and conclude that the user
needs to enter a password to authenticate.

-GAWollman