Don't create resource directories if not querying for resources

[johnSchnake]

What this PR does / why we need it:
Ordering issue in the logic caused the paths to be created even
if the queries were noops. This adds an empty-check before
creating the directories at all.

Which issue(s) this PR fixes
Related to #721

Special notes for your reviewer:

Release note:

Fixed an issue which caused some query directories to be created even if queries were not run on the namespaces corresponding to those directories.

[codecov-io]

Codecov Report

Merging #726 into master will increase coverage by 0.03%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master     #726      +/-   ##
==========================================
+ Coverage   39.97%   40.01%   +0.03%     
==========================================
  Files          69       69              
  Lines        3892     3894       +2     
==========================================
+ Hits         1556     1558       +2     
  Misses       2235     2235              
  Partials      101      101

Impacted Files	Coverage Δ
pkg/discovery/queries.go	14.11% <0%> (-0.17%)	⬇️
cmd/sonobuoy/app/status.go	60.67% <0%> (+2.24%)	⬆️

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