4DVAR observation processing, shallow water model

[arango]

The processing of the observation in the ad_main2d.F needs to be processed outside of the delayed IO time-step:

!
!  Avoid time-stepping if additional delayed IO time-step.
!
      IF (iic(ng).ne.ntstart(ng)) THEN
        ...

to allow the correct processing of observation at initialization time. This only applies to ROMS shallow water model configuration.