pybind/mgr/*: fix config_notify handling of default values

pybind/mgr/*: fix config_notify handling of default values

After 5ace82e65c72847fb875fc01c419937a26a59d70 was merged, I found
three more instances of the code being patched.

The commit message of 5ace82e65c72847fb875fc01c419937a26a59d70 was/is:

"The default values are handled by mgr_module.py's _get_module_option();
the or here means that we break any non-true (0, false, none) value and
override it with the default."

Fixes: 5ace82e65c72847fb875fc01c419937a26a59d70
Fixes: https://tracker.ceph.com/issues/43746
Signed-off-by: Nathan Cutler <ncutler@suse.com>