pybind/mgr/progress: enforced try and except on accessing event dictionary

pybind/mgr/progress: enforced try and except on accessing event dictionary

There is a certain race condition scenario where
an event gets deleted while the progress module
iterates through the ``events`` dictionary,
without a ``try and except``, this will cause
an unhandled exception error and will crash
the module.

This commit will enforce ``try and except``
on every part of the code where we are accessing
the ``events`` dictionary.

Fixes: https://tracker.ceph.com/issues/53803
Signed-off-by: Kamoltat <ksirivad@redhat.com>