Forward RUNC_FLAVOR env var down to integration tests

Update Vagrantfile and cri-integration test runner to forward
RUNC_FLAVOR to the test environment.

Allows integration tests to conditionally skip testing certain cgroup
mount setups when running against other runtimes that may not support
them yet.

Signed-off-by: Chris Henzie <chrishenzie@gmail.com>

Vagrantfile

@@ -278,6 +278,7 @@ EOF
         'GOTESTSUM_JSONFILE': ENV['GOTESTSUM_JSONFILE'],
         'GITHUB_WORKSPACE': '',
         'CGROUP_DRIVER': ENV['CGROUP_DRIVER'],
+        'RUNC_FLAVOR': ENV['RUNC_FLAVOR'] || "runc",
     }
     sh.inline = <<~SHELL
         #!/usr/bin/env bash
@@ -306,6 +307,7 @@ EOF
         'GOTEST': ENV['GOTEST'] || "go test",
         'REPORT_DIR': ENV['REPORT_DIR'],
         'CGROUP_DRIVER': ENV['CGROUP_DRIVER'],
+        'RUNC_FLAVOR': ENV['RUNC_FLAVOR'] || "runc",
     }
     sh.inline = <<~SHELL
         #!/usr/bin/env bash

script/test/cri-integration.sh

@@ -45,6 +45,10 @@ CMD=""
 if [ -n "${sudo}" ]; then
   CMD+="${sudo} "
 fi
+CMD+="env "
+if [ -n "${RUNC_FLAVOR:-}" ]; then
+  CMD+="RUNC_FLAVOR=${RUNC_FLAVOR} "
+fi
 CMD+="${PWD}/bin/cri-integration.test"
 
 ${CMD} --test.run="${FOCUS}" --test.v \