Remove non-sensical kdestroy on https stop

This kdestroy runs as root and wipes root's own ccachs ...
this is totally inappropriate.
Use a file ccache that ends up in the private tmp, so that if the
service is restarted the file is automatically removed.

https://fedorahosted.org/freeipa/ticket/6673

Signed-off-by: Simo Sorce <simo@redhat.com>
Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>
Reviewed-By: Martin Basti <mbasti@redhat.com>
Reviewed-By: Christian Heimes <cheimes@redhat.com>

install/share/ipa-httpd.conf.template

@@ -1,7 +1,7 @@
 # Do not edit. Created by IPA installer.
 
 [Service]
+Environment=KRB5CCNAME=$KRB5CC_HTTPD
 Environment=GSS_USE_PROXY=yes
 Environment=KDCPROXY_CONFIG=$KDCPROXY_CONFIG
 ExecStartPre=$IPA_HTTPD_KDCPROXY
-ExecStopPost=$POST