multiple calls of MPI app is not allowed in shell script

examples/Makefile.am

@@ -303,12 +303,14 @@ STARPU_EXAMPLES +=				\
 	cg/cg					\
 	pipeline/pipeline
 
+if !STARPU_USE_MPI_MASTER_SLAVE
 TESTS += \
 	heat/heat.sh				\
 	lu/lu.sh
 
 endif
 endif
+endif
 
 if !STARPU_SIMGRID