Feature/met on hera (#552)

## DESCRIPTION OF CHANGES: 
1. Add if condition in tests/run_experiments.sh so to get informative error message when MET and MET paths are not available on a machine.
2. Remove MET/MET+ paths in tests/baseline_configs/config.verification.sh

## TESTS CONDUCTED: 
A test run was conducted on Hera and has been finished successfully.  Another test was run on Jet, and it failed in the expected way.

## DEPENDENCIES:
To have MET verification run successfully, the observational data (e.g., CCPA, MRMS, NDAS) must be available.

## DOCUMENTATION:
N/A

## ISSUE (optional): 
This is a follow up PR to complete the previous one in https://github.com/NOAA-EMC/regional_workflow/pull/537

## CONTRIBUTORS (optional): 
@gsketefian contributed the revision.

tests/baseline_configs/config.MET_verification.sh

@@ -26,8 +26,6 @@ EXTRN_MDL_NAME_LBCS="FV3GFS"
 WTIME_RUN_FCST="01:00:00"
 
 MODEL="FV3_GFS_v15p2_CONUS_25km"
-METPLUS_PATH="/contrib/METplus/METplus-4.0.0"
-MET_INSTALL_DIR="/contrib/met/10.0.0"
 
 RUN_TASK_VX_GRIDSTAT="TRUE"
 RUN_TASK_VX_POINTSTAT="TRUE"

tests/run_experiments.sh

@@ -779,6 +779,33 @@ EXTRN_MDL_SOURCE_BASEDIR_LBCS=\"${EXTRN_MDL_SOURCE_BASEDIR_LBCS}\"
 EXTRN_MDL_FILES_LBCS=( $( printf "\"%s\" " "${EXTRN_MDL_FILES_LBCS[@]}" ))"
 
   fi
+
+#
+#-----------------------------------------------------------------------
+#
+# Set MET and MET+ paths, if necessary.
+#
+#-----------------------------------------------------------------------
+#
+  if [ "${RUN_TASK_VX_GRIDSTAT}" = "TRUE" ] || [ "${RUN_TASK_VX_POINTSTAT}" = "TRUE" ]; then 
+      if [ "$MACHINE" = "HERA" ]; then
+          met_install_dir="/contrib/met/10.0.0"
+          metplus_path="/contrib/METplus/METplus-4.0.0"
+      else
+          print_err_msg_exit "\
+The MET and MET+ paths (MET_INSTALL_DIR and MET_INSTALL_DIR) have not been specified for 
+this machine (MACHINE): MACHINE= \"${MACHINE}\" "
+      fi
+
+      str=${str}"
+#
+# MET and MET+ paths.
+#
+METPLUS_PATH=\"${metplus_path}\"
+MET_INSTALL_DIR=\"${met_install_dir}\""
+
+  fi
+
 #
 #-----------------------------------------------------------------------
 #