Merge pull request kubernetes#48571 from verult/DefaultCOSFlexDir

Automatic merge from submit-queue (batch tested with PRs 48405, 48742, 48748, 48571, 48482)

Setting default FlexVolume driver directory on COS images.

**What this PR does / why we need it**: The original default FlexVolume driver directory is not writable on COS. A new location is necessary to make FlexVolume work.

This directory doesn't exist by default. FlexVolume users need to create this directory, bind mount it, and remount with the executable permission. The other candidate is /home/kubernetes/bin, but the directory is already getting cluttered. I will submit a different PR for a script that automates this step.

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes kubernetes#48570

cluster/common.sh

@@ -743,6 +743,12 @@ EOF
   if [ -n "${FEATURE_GATES:-}" ]; then
     cat >>$file <<EOF
 FEATURE_GATES: $(yaml-quote ${FEATURE_GATES})
+EOF
+  fi
+  if [[ "${master}" == "true" && "${MASTER_OS_DISTRIBUTION}" == "gci" ]] ||
+     [[ "${master}" == "false" && "${NODE_OS_DISTRIBUTION}" == "gci" ]]; then
+    cat >>$file <<EOF
+VOLUME_PLUGIN_DIR: $(yaml-quote ${VOLUME_PLUGIN_DIR:-/home/kubernetes/flexvolume})
 EOF
   fi