Rails AR/Oracle Unit Test: [5682] failed

"bitsweat" made AR/Oracle cry...

http://dev.rubyonrails.org/changeset/5682

This is failing for Oracle not because the underlying SELECT doesn't
work, but as a side effect of the fact that allow_concurrency has been
set to true, and it's trying to do another db call (to describe the
Readers table) while a prior one is still executing.

Since this particular test doesn't seem to require allow_concurrency,
this could be refactored into a separate test case, or the below patch
fixes it as well:

Index: test/locking_test.rb