Follow-up from "WIP: Resolve "too late hook library effective unload""
The following discussion from !834 (merged) should be addressed:
there are places in premium where 'unloadLibraries' is called without calling
there are also some unittests in core: ctrl_dhcp4_srv_unittest.cc ctrl_dhcp6_srv_unittest.cc dhcp4to6_ipc_unittest.cc dhcp6to4_ipc_unittest.cc dhcp4/hooks_unittest.cc dhcp6/hooks_unittest.cc
also in all core hooks unittests.
should we also update these? it might be overkill, but doxygen explicitly mention this.
maybe call prepareUnloadLibraries from within unloadLibraries and we can easily cover all cases.