zmirror-renew-kerberos: Clean up hardcoding of user ID.
#!/bin/sh
-env KRB5CCNAME=/tmp/krb5cc_1000.tmp kinit -k -t /home/zulip/tabbott.extra.keytab tabbott/extra@ATHENA.MIT.EDU; mv /tmp/krb5cc_1000.tmp /tmp/krb5cc_1000
+krb_user_id=1051
+env KRB5CCNAME=/tmp/krb5cc_"$krb_user_id".tmp kinit -k -t /home/zulip/tabbott.extra.keytab tabbott/extra@ATHENA.MIT.EDU; mv /tmp/krb5cc_"$krb_user_id".tmp /tmp/krb5cc_"$krb_user_id"
