squash! Publish artifacts from release branches separately

Update jenkins-nightly-run.sh to allow download of builds published to
release branch directories.

tests/nightly/jenkins-nightly-run.sh

@@ -23,6 +23,7 @@ ESX_67_VERSION="ob-8169922"
 VC_67_VERSION="ob-8217866"
 
 DEFAULT_LOG_UPLOAD_DEST="vic-ci-logs"
+DEFAULT_VCH_BRANCH=""
 DEFAULT_VCH_BUILD="*"
 DEFAULT_TESTCASES=("tests/manual-test-cases/Group5-Functional-Tests" "tests/manual-test-cases/Group13-vMotion" "tests/manual-test-cases/Group21-Registries" "tests/manual-test-cases/Group23-Future-Tests")
 
@@ -45,7 +46,8 @@ testcases=("${@:-${DEFAULT_TESTCASES[@]}}")
 # TODO: the version downloaded by this logic is not coupled with the tests that will be run against it. This should be altered to pull a version that matches the commit SHA of the tests
 # we will be running or similar mechanism.
 VCH_BUILD=${VCH_BUILD:-${DEFAULT_VCH_BUILD}}
-input=$(gsutil ls -l gs://vic-engine-builds/${VIC_BINARY_PREFIX}${VCH_BUILD} | grep -v TOTAL | sort -k2 -r | head -n1 | xargs | cut -d ' ' -f 3 | cut -d '/' -f 4)
+VCH_BRANCH=${VCH_BRANCH:-${DEFAULT_VCH_BRANCH}}/
+input=$(gsutil ls -l gs://vic-engine-builds/${VCH_BRANCH#/}${VIC_BINARY_PREFIX}${VCH_BUILD} | grep -v TOTAL | sort -k2 -r | head -n1 | xargs | cut -d ' ' -f 3 | cut -d '/' -f 4)
 
 # strip prefix and suffix from archive filename
 VCH_BUILD=${input#${VIC_BINARY_PREFIX}}