adds mpi barrier to ensure all pIDs are recieved

this is a fix for #155 with some additional assertions for sanity checking.
23 jobs for koch/fix-reverse-distribution in 183 minutes and 27 seconds (queued for 38 seconds)
latest
Name Stage Failure
failed
clang_10.0_mpionly_eigen_petsc_trilinos Pretest The script exceeded the maximum execution time set for the job
175/252 Test #176: PrimitiveMigrationConvergenceTest1 .........   Passed    1.13 sec
Start 177: PrimitiveMigrationConvergenceTest3
176/252 Test #177: PrimitiveMigrationConvergenceTest3 ......... Passed 0.75 sec
Start 178: PrimitiveMigrationConvergenceTest4
177/252 Test #178: PrimitiveMigrationConvergenceTest4 ......... Passed 0.75 sec
Start 179: PrimitiveStorageCopyTest1
178/252 Test #179: PrimitiveStorageCopyTest1 .................. Passed 0.15 sec
Start 180: PrimitiveStorageCopyTest3
ERROR: Job failed: execution took longer than 3h0m0s seconds
failed
gcc_10_mpionly_dbg_sp Pretest The script exceeded the maximum execution time set for the job
136/197 Test #136: PrimitiveMigrationConvergenceTest1 .........   Passed   10.91 sec
Start 137: PrimitiveMigrationConvergenceTest3
137/197 Test #137: PrimitiveMigrationConvergenceTest3 ......... Passed 5.73 sec
Start 138: PrimitiveMigrationConvergenceTest4
138/197 Test #138: PrimitiveMigrationConvergenceTest4 ......... Passed 5.08 sec
Start 139: PrimitiveStorageCopyTest1
139/197 Test #139: PrimitiveStorageCopyTest1 .................. Passed 0.37 sec
Start 140: PrimitiveStorageCopyTest3
ERROR: Job failed: execution took longer than 3h0m0s seconds