bitbake: gitsmy.py: Fix unpack of submodules of submodules

bitbake: gitsmy.py: Fix unpack of submodules of submodules

If the submodule is in a subdirectory, it needs to have that structure
preserved.  This means the unpack path needs to be in the 'dirname' of the
final path -- since the unpack directory name is specified in the URI.

Additional specific test cases were added to ensure this is working properly
based on two recent error reports.

(Bitbake rev: 8c8ecec2a722bc2885e2648d41ac8df07bdf660d)

Signed-off-by: Mark Hatle <mark.hatle@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>