In the commit 622d3ddb92
"Fixed test and moved constants into standalone func" the minimum CPU
resource value for a job was increased from 100 to 20.
This can break the nomad setup for people that used lower CPU
values and are at the maximum MHz value of the available CPU on a
machine.
Change the minimum back to 20 MHz to ensure downwards compatibility.
In #3520, work was done to true up the defaults for Nomad resource
stanzas with the documentation. This fixes the tests that I
accidentally broke in the process. Some questions were raised about
using dynamic elements as part of expects, which is why I opted to
copy the MinResources pattern. During this refactor I also noticed
that structs.go had a similar issue and an inconsistent minium for CPU.
