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-build.sh

@@ -22,6 +22,8 @@ export GO111MODULE=on
 export GOGC=25
 export ENABLE_ADMIN=1
 
+export MINIO_CI_CD=1
+
 MINIO_CONFIG_DIR="$WORK_DIR/.minio"
 MINIO=( "$PWD/minio" --config-dir "$MINIO_CONFIG_DIR" )