[Android] Try to use shared mode when CPU arch mismatches

Shared mode for crosswalk is sharing java classes and
native libraries. Previously, it will try to find library
only if internal java classes are not found.
This commit extends the condition to handle CPU arch
mismatches. In that case, java classes are available but
native library is not.

Implement this by move the loading of native library ahead
to the initialization of reflection layer.

BUG=https://crosswalk-project.org/jira/browse/XWALK-2633
Merge pull request #2464 from wang16/shared_on_so_missing

[Android] Try to use shared mode when CPU arch mismatches