[BUG] Core-daemon does not search for `zebra` executable in the correct path

[fabrc]

Describe the bug
FRRzebra service is not loaded during startup because daemon/core/services/manager.py fails to locate the zebra executable in the correct path.

To Reproduce
Steps to reproduce the behavior:

1. On Debian 12, install frr package using:

apt install -y frr

2. Install core_9.2.1_amd64.deb
3. Start core-daemonusing:

systemctl start core-daemon

or, to see the error message:

source /opt/core/venv/bin/activate
core-daemon --debug

5. See error:

2025-07-07 16:52:42,314 - DEBUG - manager:load_locals - not loading service(zebra): service(zebra): failed to find required executable(zebra) in path

Expected behavior
Error message should not apear.

Desktop (please complete the following information):

• OS: Debian 12
• CORE Version 9.2.1

Additional context
The bug is due to the fact that, in order to add the FRRzebra service to the daemon session, daemon/core/services/manager.py uses the function utils.which to search for the zebraexecutable. But the function call does not take into account the frr_sbin_path variable that is configured in the FRRZebra class.

References

• https://github.com/coreemu/core/blob/master/daemon/core/services/manager.py#L71
• https://github.com/coreemu/core/blob/master/daemon/core/services/defaults/frrservices/services.py#L101