tutorials: Use getApplication to set the application rather than hard-coding it

tutorials/discreteMethods/molecularDynamics/mdEquilibrationFoam/Allrun

@@ -5,8 +5,6 @@ cd ${0%/*} || exit 1    # run from this directory
 # Source tutorial run functions
 . $WM_PROJECT_DIR/bin/tools/RunFunctions
 
-application="mdEquilibrationFoam"
-
 for caseName in periodicCubeArgon periodicCubeWater
 do
 (
@@ -14,7 +12,7 @@ do
 
     runApplication blockMesh
     runApplication mdInitialise
-    runApplication $application
+    runApplication `getApplication`
 )
 done
 # ----------------------------------------------------------------- end-of-file