oat_file_manager: Avoid global collision check.

Avoid the global collision check in case we encounter a classloader
that we don't recognize. This seems overly conservative. Instead, trust
that the classloader does the right thing.

Bug: 36480683
Bug: 37777332

Test: make test-art-host
Test: manual testing

(cherry picked from commit 04aa213e96c1095e8d1e07cbc426d009777de241)

Change-Id: I45ca1a12c14ba303bd27e9463e612f7c73c778ec