message: Only do native lookup if it's supported
  Also fix as bug where we were checking the wrong field to check
  for native/virtual support: oops.
diff: @@ -264,7 +264,7 @@ export default class CallHandler extends EventEmitter {
  }
  public getSupportsVirtualRooms() {
  - return this.supportsPstnProtocol;
  + return this.supportsSipNativeVirtual;
  }
  public pstnLookup(phoneNumber: string): Promise<ThirdpartyLookupResponse[]> {
  @@ -883,10 +883,15 @@ export default class CallHandler extends EventEmitter {
  // Now check to see if this is a virtual user, in which case we should find the
  // native user
  + let nativeUserId;
  + if (this.getSupportsVirtualRooms()) {
  const nativeLookupResults = await this.sipNativeLookup(userId);
  const lookupSuccess = nativeLookupResults.length > 0 && nativeLookupResults[0].fields.lookup_success;
  - const nativeUserId = lookupSuccess ? nativeLookupResults[0].userid : userId;
  + nativeUserId = lookupSuccess ? nativeLookupResults[0].userid : userId;
  console.log("Looked up " + number + " to " + userId + " and mapped to native user " + nativeUserId);
  + } else {
  + nativeUserId = userId;
  + }
  const roomId = await ensureDMExists(MatrixClientPeg.get(), nativeUserId);
  