message: Fix BriefcaseManager mocks to use renamed
  _imodelClient property.
diff: @@ -130,7 +130,7 @@ export class MockAssetUtil {
  MockAssetUtil.setupConnectClientMock(connectClientMock, assetDir);
  MockAssetUtil.setupIModelHubClientMock(iModelHubClientMock, assetDir);
  - (BriefcaseManager as any)._hubClient = iModelHubClientMock.object;
  + (BriefcaseManager as any)._imodelClient = iModelHubClientMock.object;
  // Get test projectId from the mocked connection client
  const project: Project = await connectClientMock.object.getProject(accessToken as any, {
  @@ -163,7 +163,7 @@ export class MockAssetUtil {
  }
  public static tearDownOfflineFixture() {
  - (BriefcaseManager as any)._hubClient = undefined;
  + (BriefcaseManager as any)._imodelClient = undefined;
  }
  /** Setup functions for the ConnectClient mock */
  