ShellPkg/HandleParsingLib: Open LoadedImageProtocol first

This patch changes the order of operations to make sure we can open the
LoadedImageProtocol before getting the format string. This should not
affect functionality, and makes the next patch easier to review.

Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Jaben Carsey <jaben.carsey@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Westfahl <jeff.westfahl@ni.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>