Fix potential linear alloc memory leak

Previously, if we created a linear alloc for a class loader but
never created the class table, the linear alloc would never get
freed since it would have no corresponding ClassLoaderData.

Fixes valgrind-test-art-host-gtest-oat_test

Bug: 27384882
Change-Id: Ic8f35b58c3117127a39521b6b9d25ef12c72040c
3 files changed