Merge branch 'ndk/machinefiles/cori-pelayouts-atm2' (PR #2216)

Adjust PE layouts to limit total number of tasks in ATM to be less than or equal
to the total number of elements.This helps avoid error with GNU and was overall
insignificant impact to performace. Affected cori-knl layouts and one edison layout.

Add more nodes to ne4 layouts on NERSC machines to improve thruput for the
ultralowres tests. Also add a small size for cori-knl.

Add default layouts for G cases 60to30 and 18to6 on cori-knl for testing