MaaS: Pin psutil to 1.2.1 or less
MaaS: Pin psutil to 1.2.1 or less

The psutil module has undergone a complete rewrite of sorts after
version 1.x and this patch sets a pin to keep it at 1.2.1 or less.
This matches OpenStack's upper requirement in newton.

Connects rcbops/rpc-openstack#1984

shannonmitchell/rpc-openstack,rcbops/rpc-openstack,git-harry/rpc-openstack,galstrom21/rpc-openstack,BjoernT/rpc-openstack,cloudnull/rpc-openstack,cloudnull/rpc-openstack,robb-romans/rpc-openstack,hughsaunders/rpc-openstack,BjoernT/rpc-openstack,robb-romans/rpc-openstack,rcbops/rpc-openstack,git-harry/rpc-openstack,major/rpc-openstack,mancdaz/rpc-openstack,prometheanfire/rpc-openstack,prometheanfire/rpc-openstack,mancdaz/rpc-openstack,shannonmitchell/rpc-openstack,hughsaunders/rpc-openstack,cfarquhar/rpc-openstack,major/rpc-openstack,galstrom21/rpc-openstack,jacobwagner/rpc-openstack,cfarquhar/rpc-openstack,jacobwagner/rpc-openstack