CA-147141: Fix includes in tapdisk-interface.h

As tapdisk-interface.h was referencing to types which were not defined,
so automatic mock creation failed. With this fix, the file should
compile on its own.

Signed-off-by: Mate Lakat <mate.lakat@citrix.com>
Reviewed-by: Thanos Makatos <thanos.makatos@citrix.com>
CA-147141: Move declarations to source file

These inline methods were declared in the header file, and the unit
testing framework failed to create mock implementations. Moving the
declarations to the source file to avoid this problem.

Signed-off-by: Mate Lakat <mate.lakat@citrix.com>
Reviewed-by: Thanos Makatos <thanos.makatos@citrix.com>
CA-147141: Add example noop unit tests

Signed-off-by: Mate Lakat <mate.lakat@citrix.com>
Reviewed-by: Thanos Makatos <thanos.makatos@citrix.com>
CA-147141: Test tapdisk_xenblkif_complete_request

Signed-off-by: Mate Lakat <mate.lakat@citrix.com>
Reviewed-by: Thanos Makatos <thanos.makatos@citrix.com>
CA-147141: Rename test methods, add documentation

blktap is using the underscore convention, so using the same notation in
the tests as well. Also added some comments to explain the tests.

Signed-off-by: Mate Lakat <mate.lakat@citrix.com>
Reviewed-by: Thanos Makatos <thanos.makatos@citrix.com>
Merge branch 'CA-147141' into xs64bit

GitHub: closes #131 on xapi-project/blktap