android: Fix up double-callback of Echo plugin.
android: Fix up double-callback of Echo plugin.

corimf/cordova-mobile-spec,apache/cordova-mobile-spec,ollie314/cordova-mobile-spec,ollie314/cordova-mobile-spec,apache/cordova-mobile-spec,ollie314/cordova-mobile-spec,apache/cordova-mobile-spec,corimf/cordova-mobile-spec,corimf/cordova-mobile-spec,corimf/cordova-mobile-spec,corimf/cordova-mobile-spec,apache/cordova-mobile-spec,ollie314/cordova-mobile-spec,ollie314/cordova-mobile-spec,apache/cordova-mobile-spec