led-use-json: Use specific config files

- When enabled `led-use-json`, it should use the JsonConfig class to
  find the JSON file name, and do not start until JSON config is
  found.

- If it has to wait for the IBMCompatible interface to show up on
  D-bus first, it will wait for that.

Tested:
- If there is a `/etc/phosphor-led-manager/led-group-config.json`
  path, congfile=/etc/phosphor-led-manager/led-group-config.json
- If there is a `/usr/share/phosphor-led-manager/led-group-config.json`
  path and there is not `/etc/phosphor-led-manager/`,
  congfile=/usr/share/phosphor-led-manager/led-group-config.json
- If the above two paths do not exist, get the `Name` property of the
  `xyz.openbmc_project.Configuration.IBMCompatibleSystem` interface,
  congfile=/usr/share/phosphor-led-manager/${Name}/led-group-config.json

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: I1528a3d3711ef6b604868387ad42cb3c0afde119
9 files changed