Avoid path conflicts for the notice files

Path conflicts could happen when following conditions are met.
1) a java library named "foo" is not installable.
2) a java library named "bar" is installable, and its stem is set to
"foo".

Then the notice file for 1) becomes foo.jar.txt following its
LOCAL_MODULE, while the notice file for 2) becomes foo.jar.txt following
its stem. Since the file for 1) is a synthetic one, the actual name
isn't important. Avoid the conflict by appending a suffix
(_non_installable, but could be anything) to the file name for 1).

There still is a chance for the conflict; if the stem for "bar" is set
to "foo_non_installable". But practically, the chances are very low.

Bug: 139391334
Bug: 143700028
Test: m
Change-Id: Id50b30774bbf65cc180baf963a95ea56fe6eb74f