mgmt: hawkbit: hawkbit_autohandler_wait() returns to early

[maass-hamburg]

Describe the bug
the k_event_clear in the work might be to late sometimes, when
hawkbit_autohandler_wait() is executed directly after
hawkbit_autohandler(). This leads to getting the events
of the former execution and also not waiting until the
current autohandler run is finished.

To Reproduce
Steps to reproduce the behavior:

1. west build -p -b stm32h573i_dk samples/subsys/mgmt/hawkbit -- -DCONF_FILE="prj.conf overlay-runtime.conf" && west flash
2. let the autohandler run by it self
3. hawkbit run
4. See error ( the shell command returns directly and doesn't block, also the return value is the one from the previous run)

Expected behavior
the shell command should block until the requested execution is completed

Impact
as long as hawkbit_autohandler_wait() is just used to wait for the first start, it shouldn't be a problem. For the shell it would mostly just result, in some misleading shell output.

[dkalowsk]

@maass-hamburg can you please use the bug template to fill out the missing information for others looking at the issue.

[maass-hamburg]

@maass-hamburg can you please use the bug template to fill out the missing information for others looking at the issue.

Sure