fault-monitor: remove locally generated errors

Switch fault-monitor to use Common.Errors instead of locally defined
ones.  This greatly simplifies the build structure and follows the
expected phosphor-logging patterns better.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Idb3473989c86b3a505f3c0a238735db6f3a4349e
19 files changed