[exercise fluidsystem] change name of input files in solution to match to executables

exercises/solution/exercise-fluidsystem/CMakeLists.txt

@@ -3,13 +3,13 @@
 dune_add_test(NAME exercise-fluidsystem_a_solution
               SOURCES exercise-fluidsystem.cc
               COMPILE_DEFINITIONS TYPETAG=ExerciseFluidsystemTwoPTypeTag
-              CMD_ARGS exercise-fluidsystem_a.input)
+              CMD_ARGS exercise-fluidsystem_a_solution.input)
 
 #part b: 2p2cproblem
 dune_add_test(NAME exercise-fluidsystem_b_solution
               SOURCES exercise-fluidsystem.cc
               COMPILE_DEFINITIONS TYPETAG=ExerciseFluidsystemTwoPTwoCTypeTag
-              CMD_ARGS exercise-fluidsystem_b.input)
+              CMD_ARGS exercise-fluidsystem_b_solution.input)
 
 # add exercises to the common target
 add_dependencies(test_exercises exercise-fluidsystem_a exercise-fluidsystem_b)