Validate the priority of an LED is same

Need to make sure that the priority of a particular LED is the same
across all groups, it needs to throw the std::runtime_error if not
the same.

Tested: Manually changed the JSON file to have priority of a particular
LED different across groups and saw ledManager throw a runtime exception
and failed to run.

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: I9d3e788dd86defb9a781dc958976b51ec7d3fd19
2 files changed