Fix thsmi#799 - Sieve as a Thunderbird plug broken

- Accommodate nsIMsgIncomingServer interface change
- https://hg.mozilla.org/comm-central/rev/e7602ee8cf16b8885dcc63d6f70650223b26260f

src/wx/api/sieve/SieveAccountsApi.js

@@ -61,11 +61,17 @@
             },
 
             async getUsername(id) {
-              return await getIncomingServer(id).realUsername;
+							const retval =
+								await getIncomingServer(id).realUsername ||
+								await getIncomingServer(id).username;
+              return retval;
             },
 
             async getHostname(id) {
-              return await getIncomingServer(id).realHostName;
+							const retval =
+								await getIncomingServer(id).realHostName ||
+								await getIncomingServer(id).hostName;
+              return retval;
             }
           }
         }