Add tests for checkpoint mesh reads

Based heavily on @friedmud's test in idaholab#8472; adds test coverage for
issue idaholab#7752, for both ASCII and binary CheckpointIO pre-split mesh
reads.

test/tests/mesh/checkpoint/checkpoint_split.i

@@ -0,0 +1,42 @@
+[Mesh]
+  type = FileMesh
+  file = checkpoint_split_in.2.cpr
+[]
+
+[Variables]
+  [./u]
+  [../]
+[]
+
+[Kernels]
+  [./diff]
+    type = Diffusion
+    variable = u
+  [../]
+[]
+
+[BCs]
+  [./left]
+    type = DirichletBC
+    variable = u
+    boundary = left
+    value = 0
+  [../]
+  [./right]
+    type = DirichletBC
+    variable = u
+    boundary = right
+    value = 1
+  [../]
+[]
+
+[Executioner]
+  type = Steady
+  solve_type = 'PJFNK'
+  petsc_options_iname = '-pc_type -pc_hypre_type'
+  petsc_options_value = 'hypre boomeramg'
+[]
+
+[Outputs]
+  exodus = true
+[]

test/tests/mesh/checkpoint/checkpoint_split_in.2.cpa

@@ -0,0 +1,5 @@
+checkpoint-1.1	 # version
+2	 # dimensions
+1	 # parallel
+2	 # n_procs
+0	 # subdomain id to name map