Fix the protocol order on the server side

the server protocol order precedes over the client order. Therefore if the server is `unix sss krb5`  and th
e client `krb5 unix` the client will authenticate on the mgm using unix, and the created file belongs to `nobody`, but the file transfert can continue with unix and you get a file full of data belonging to nobody. If the client keeps only `krb5` then you get an ampty file belonging to the correct user...

continuousintegration/docker/ctafrontend/cc7/config/ctaeos/etc/xrd.cf.mgm

@@ -21,9 +21,13 @@ sec.protocol sss -c /etc/eos.keytab -s /etc/eos.keytab
 #sec.protocol krb5 host/<host>@CERN.CH
 sec.protocol krb5 /etc/eos.krb5.keytab eos/eos-server@TEST.CTA
 
-sec.protbind localhost.localdomain unix sss
-sec.protbind localhost unix sss
-sec.protbind * only sss unix krb5
+#sec.protbind localhost.localdomain unix sss
+#sec.protbind localhost unix sss
+# wrong order: can only get empty files owned by the correct user or 
+# files with data belonging to nobody...
+#sec.protbind * only sss unix krb5
+# krb5 first then the rest and I believe that we do not need unix
+sec.protbind * only krb5 sss
 ###########################################################
 mgmofs.fs /
 mgmofs.targetport 1095