patman: fix class TestFunctional

patman: fix class TestFunctional

Variable orig_dir cannot be used in the finally block if it has not be
assigned outside of the try block.

tools/patman/func_test.py:523:21:
E0601: Using variable 'orig_dir' before assignment
(used-before-assignment)

tools/patman/func_test.py:691:21:
E0601: Using variable 'orig_dir' before assignment
(used-before-assignment)

Fixes: fd70986a62af ("patman: Add a test that uses gitpython")
Fixes: be051c0c7741 ("patman: Detect missing upstream in CountCommitsToBranch")
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>