commit() when autocommit is enabled

[Scott Anderson]

I'm working on a path to add generated PK support to SQLite, but I've
come across an issue with commit() - for some reason, autocommit is on,
but Cayenne is still trying to call commit(), which causes an exception.
An effective workaround is to re-check getAutoCommit() in
ConnectionWrapper.commit() before calling connection.commit(), but I'm
curious to know whether this behavior is actually even illegal to begin
with, and if so, whether Cayenne already attempts to avoid this case.