Update .travis.yml (#561)

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Pull Request resolved: #561

Reviewed By: stoyan

Differential Revision: D15446847

Pulled By: jingping2015

fbshipit-source-id: 70e984096dadaf774f9a871df3360c01a3f0f103

.travis.yml

@@ -11,6 +11,7 @@ licenses:
 - android-sdk-license-.+
 - google-gdk-license-.+
 
+dist: trusty
 
 before_install:
 - yes | sdkmanager "platforms;android-27"