fix checkout branch java-chassis-1.x error (#116)

diff --git a/.travis.yml b/.travis.yml
index b999a93..70f1734 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,7 +3,7 @@
   - gitbook build java-chassis-reference docs/java-chassis
   - gitbook build saga-reference docs/saga
   - gitbook build service-center-reference docs/service-center
-  - git checkout -B java-chassis-1.x
+  - git checkout -B java-chassis-1.x java-chassis-1.x
   - gitbook build java-chassis-reference docs/java-chassis/1.x
   - git clone --depth=10 --branch=master https://$PUSH_TARGET_URL servicecomb-java-chassis-doc
 after_success: