[Android] Remove the wrong dependence in runtime client test apk.

This patch will resolve the issue about wrong dependence in the runtime
client test apk.
In file CrossPackageWrapper.java, the constructor function "CrossPackageWrapper()"
has the judgement about the class load, which mode(embedded, shared) was used based
on the result of the class(XWalkRuntimeView) loaded. In shared mode, the core shell
is not needed for the runtime client test shell. So removed it, otherwise it will
lead to the instrumentation test crashed in shared mode.

BUG=#916