qemu: Move qemu/provider_lib -> provider

This is a leftover from the previous specification of
a test provider. In fact, the common provider lib should
be at top level, and the name of the lib is provider,
not provider_lib. Fix tests accordingly.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
Merge pull request #13 from autotest/provider-libs

qemu: Move qemu/provider_lib -> provider