Always check for root disks unless MINIO_CI_CD is set (#14232)

The current code considers a pool with all root disks to be as part
of a testing environment even if there are other pools with mounted
disks. This will result to illegitimate writing in root disks.

Fix this by simplifing the logic: require MINIO_CI_CD in order to skip
root disk check.

buildscripts/verify-healing.sh

@@ -17,6 +17,7 @@ function start_minio_3_node() {
     export MINIO_ROOT_USER=minio
     export MINIO_ROOT_PASSWORD=minio123
     export MINIO_ERASURE_SET_DRIVE_COUNT=6
+    export MINIO_CI_CD=1
 
     start_port=$2
     args=""