Log Message:
security/heimdal: Prefix kerberos commands by default

It has long been an issue that heimdal installs "su" which shadows
system su and behaves differently.  Now, with openssl 1.1, many people
are getting heimdal installed that did not expect it or ask for it.

(Really, heimdal should be split into libraries and apps, so that
programs can have kerberos support without adding commands to the
user's namespace, but this is vastly easier.)

(In response to on-list complaints, and believing this will not be
contoversial.)