Work around PETSc bug in set_local_assembly
Work around PETSc bug in set_local_assembly

PETSc ignores the flag value for MAT_IGNORE_OFF_PROC_ENTRIES if the
matrix is of type MPIAIJ and unilaterally sets the option to
PETSC_TRUE.  Since we don't want to do that if flag is .false. don't
bother setting the option at all in that case.

jrper/fluidity,jrper/fluidity,jrper/fluidity,iakovos-panourgias/fluidity,jjo31/ATHAM-Fluidity,rjferrier/fluidity,rjferrier/fluidity,iakovos-panourgias/fluidity,jrper/fluidity,iakovos-panourgias/fluidity,jjo31/ATHAM-Fluidity,iakovos-panourgias/fluidity,jjo31/ATHAM-Fluidity,rjferrier/fluidity,jrper/fluidity,jjo31/ATHAM-Fluidity,rjferrier/fluidity,jjo31/ATHAM-Fluidity,iakovos-panourgias/fluidity,rjferrier/fluidity