Fix sonobuoy conformance testing

[dereknola]

Proposed Changes

See failures on the nightly runs around

sonobuoy run --config=scripts/sonobuoy-config.json --plugin-env=e2e.E2E_USE_GO_RUNNER=true --kubernetes-version= --wait=90 '--e2e-focus=\[Serial\].*\[Conformance\]'

[SERIAL-mysql] Error: invalid argument "" for "--kubernetes-version" flag: version "" is invalid: Malformed version: 

At some point the VERSION_K8S stopped getting passed correctly down the script layers to the actual sonobuoy call.
We just need to properly export this so its available to the subprocess.

Types of Changes

Verification

Manually run locally and SERIAL and PARALLEL tests now correctly launch.

Testing

Linked Issues

#11714

User-Facing Change

Further Comments

We can't move forward with GHA migration until we are in a stable place with the old tests.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 45.15%. Comparing base (9604f27) to head (f87235a).
Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #12214      +/-   ##
==========================================
+ Coverage   45.13%   45.15%   +0.02%     
==========================================
  Files         188      188              
  Lines       19219    19221       +2     
==========================================
+ Hits         8675     8680       +5     
+ Misses       9310     9308       -2     
+ Partials     1234     1233       -1     

Flag	Coverage Δ
e2etests	35.67% <ø> (+0.04%)	⬆️
inttests	34.75% <ø> (-0.07%)	⬇️
unittests	19.81% <ø> (+<0.01%)	⬆️

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