ipa-uuid: emit a message when unexpected mod type is encountered

This patch is related to the following defect reported by covscan of FreeIPA
master code:

"""
Error: DEADCODE (CWE-561): /daemons/ipa-slapi-plugins/ipa-uuid/ipa_uuid.c:796:
cond_const: Condition "modtype != 1", taking false branch. Now the value of
"modtype" is equal to 1.
/daemons/ipa-slapi-plugins/ipa-uuid/ipa_uuid.c:796:
cond_const: Condition "modtype != 4", taking false branch. Now the value of
"modtype" is equal to 4.
/daemons/ipa-slapi-plugins/ipa-uuid/ipa_uuid.c:941:
equality_cond: Jumping to case "1".
/daemons/ipa-slapi-plugins/ipa-uuid/ipa_uuid.c:957: equality_cond: Jumping to
case "4".
/daemons/ipa-slapi-plugins/ipa-uuid/ipa_uuid.c:940: intervals: When
switching on "modtype", the value of "modtype" must be in one of the following
intervals: {[1,1], [4,4]}.
/daemons/ipa-slapi-plugins/ipa-uuid/ipa_uuid.c:940: dead_error_condition: The
switch value "modtype" cannot reach the default case.
/daemons/ipa-slapi-plugins/ipa-uuid/ipa_uuid.c:1031: dead_error_begin:
Execution cannot reach this statement: "default:".
"""

The patch is a part of series related to
https://fedorahosted.org/freeipa/ticket/4795

Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>

daemons/ipa-slapi-plugins/ipa-uuid/ipa_uuid.c

@@ -1030,6 +1030,8 @@ static int ipauuid_pre_op(Slapi_PBlock *pb, int modtype)
 
         default:
             /* never reached, just silence compiler */
+            LOG_TRACE("File '%s' line %d: Got unexpected value of modtype:"
+                      "%d\n", __FILE__, __LINE__, modtype);
             break;
         }