Check that uuid is in the description, otherwise skip.

In this case we've found that different versions of OpenVZ may
include output for this vzlist command (e.g., just a -) if there
aren't any instances. We just want to ignore these if the json
isn't there as expected (since _set_description is what should
construct them in the first place).

Change-Id: I472bbb63afe1313e74b742297320bf0adebacc32
Merge "Check that uuid is in the description, otherwise skip."