Run g-w linker script before ctest for prepoceanobs task (#1034)

In anticipation of the merging of
NOAA-EMC/global-workflow#2459 , the
`test_gdasapp_soca_setup_obsprep` ctest which sets up for
`test_gdasapp_soca_JGLOBAL_PREP_OCEAN_OBS` now runs the global-workflow
`sorc/link_workflow.sh` script to allow the observation config files to
be accessed in a global-workflow-compliant way.

Effectively addresses #1032

test/soca/gw/setup_obsprep.sh

@@ -13,6 +13,9 @@ project_source_dir="$1"
 testdatadir="${project_source_dir}/test/soca/testdata"
 testdatadir_bufr="${project_source_dir}/build/gdas/test/testdata"
 
+# run the g-w link script so that the config files can be found
+(cd ${project_source_dir}/../../.. && ./link_workflow.sh)
+
 # Clean up previous attempts
 rm -rf gdas.20180414  gdas.20180415