CentOS packages that has this binary:
/usr/bin/mpiexec
/usr/lib64/mpich2/bin/mpiexec
/usr/lib/mpich2/bin/mpiexec
/usr/lib64/mpich/bin/mpiexec
/usr/lib/mpich/bin/mpiexec
/usr/lib64/mvapich2-psm/bin/mpiexec
/usr/lib64/mvapich2/bin/mpiexec
/usr/lib/mvapich2/bin/mpiexec