Make sure that UUIDs when null upstream are printed as empty and not as all 0s

[perigrin]

ether| perigrin: ew, conch on the v2 api fills in all 0 uuids for device location when it doesn't exist.. please don't replicate that in kosh for v3
ether| that is, compare conch api get /device/A352777X8B11547 | json to conch --json device A352777X8B11547 get | json -- see all the zeros for location info

This may be difficult because Go (kinda similar to Perl) has an opinion that all variables should have a value. There is a default value and for UUIDs that may be all 0s. We will need to detect the difference and key off of that somehow.

[karenetheridge]

It would be even better to leave out empty sections entirely, if possible.