phosphor-watchdog: Cleanup CodeChecker Errors

Removed the following error messages:
bugprone-unused-raii
  - object destroyed immediately after creation; did you mean to name
  the object
performance-move-const-arg
  - std::move of the variable 'maybeFallback' of the trivially-copyable
  type 'std::optional' has no effect; remove std::move()
clang-diagnostic-inconsistent-missing-override
  - 'interval' overrides a member function but is not marked 'override'

Change-Id: I0f6ab3002b7175a73449d58ea6ae6b66f7c851ef
Signed-off-by: Willy Tu <wltu@google.com>
3 files changed