FirmwareVolume.UnDispatchedFfsDict is mutated during iteration,
convert the FirmwareVolume.UnDispatchedFfsDict.keys() to a new list
to resolve this problem.
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>