dump non parallel matrix

[guignont]

When dumping a non parallel matrix the code exit with a petsc error:
*I-Internal Converting DoKMatrix: 0x784e50 to SimpleCSRMatrix: 0x7887b0
*I-Internal Converting SimpleCSRMatrix: 0x7887b0 to PETScMatrix 0x785be0
*I-Internal Matrix range : [0:99]
[0]PETSC ERROR: --------------------- Error Message --------------------------------------------------------------
[0]PETSC ERROR: Argument out of range
[0]PETSC ERROR: Comm must be of size 1

It can be reproduced with (in RedistributorAlgebraTestFramework)

Alien::RedistributedMatrix Aa(A, redist);
if(Environment::parallelMng()->commRank() == 0)
    dump(Aa);