EKS Raid Disk Startup Script for Local PV fails if Disk is Already Mounted

[kevinliu24]

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Describe the bug (required)

The EKS Raid disk script for local PV below errors out if the raid disk we need to mount is already mounted.
https://raw.githubusercontent.com/vesoft-inc/nebula-operator/v1.8.0/config/samples/raid-disks/eks-daemonset-raid-disks.yaml

We need to check if the disk we need to mount is not already mounted before trying to mount the disk. We should only error out if a disk other then the disk we want to mount is already mounted to the mountpoint.

Your Environments (required)

• OS: uname -a
• Commit id (e.g. a3ffc7d8)

How To Reproduce(required)

Steps to reproduce the behavior:

1. Easiest way to reproduce is to deploy the script twice.

Expected behavior

The eks raid disk script should not fail due to double mount.

Additional context

https://nebula-graph.atlassian.net/browse/NGSR-231