In this patch we add some unit tests for exception cases
to improve overall test coverage. Tests added:
test_share_set_visibility_exception
test_share_set_property_exception
test_share_unset_name_exception
test_share_unset_property_exception
Change-Id: I7604da8943dca8f3eada7c5ac1311086772f41a5
Partially-implements: bp openstack-client-support