[SysApps][Android] Fix several issues on messaging api

1) Correct addEventListener from "messaging" to "messaging.sms".
2) Each PendingIntent should have different requestCode to identify itself. If
using same code, the extra data field of PendingIntent instance will be replaced
by the new one. Then system calls the intent callback function only once.
3) In unit test page, move the verification steps into send.then
callback instead of calling after send function.

BUG=https://crosswalk-project.org/jira/browse/XWALK-940