libtt: Resolve coverity warnings

cde/lib/tt/lib/api/c/api_file.C

@@ -426,9 +426,8 @@ _ttds_file_server(const char *filename, const char **hostname)
 	_Tt_string	hostname_s;
 	_Tt_string	partition;
 	_Tt_string	network_path;
-	
-	*hostname = "";
-	if (filename==0 || hostname==0) {
+
+	if (filename == NULL || hostname == NULL) {
 		return TT_ERR_POINTER;
 	}
 	filename_s = filename;

cde/lib/tt/lib/api/c/api_message.C

@@ -2476,7 +2476,7 @@ _tt_message_context_bval(Tt_message m, const char *slotname,
 	}
 	*len = value.len();
 	*val = (unsigned char *)_tt_strdup( value, *len );
-	if (val == 0) {
+	if (*val == NULL) {
 		return TT_ERR_NOMEM;
 	}
 	return TT_OK;

cde/lib/tt/lib/mp/mp_auth.C

@@ -291,6 +291,8 @@ write_auth_file(char *filename)
     else
       (void) unlink(tmpnam);
 
+    free(tmpnam);
+
     return TT_OK;
 }
 Tt_status _Tt_auth::
@@ -306,7 +308,10 @@ retrieve_auth_cookie()
       return TT_AUTHFILE_ENTRY_MISSING;
 
     buff = (char*) malloc(entry->auth_data_length + 1);
-    if (NULL == buff) return TT_ERR_NOMEM;
+    if (NULL == buff) {
+        _tt_FreeAuthFileEntry(entry);
+        return TT_ERR_NOMEM;
+    }
 
     strncpy(buff, entry->auth_data, entry->auth_data_length);
     buff[entry->auth_data_length] = '\0';