Refactor setting up network storage and run setup network storage as root

[harshthakkar01]

This PR does the following.

• Refactor setup_network_storage function and setupnfs-exports into separate file.
• Adds wrapper around setup-network-storage package to run it as root.
• Gives slurm user permission to run bash scripts as root.
• During setup_network_storage stage, fetches new config from the local. If used like previously, it would fetch old config.
• Also from the discussion with SchedMD people, it was mentioned to also run setup_nfs_exports in the controller during reconfigure.

Manual testing

Deployed a cluster without any network storage and then reconfigured after adding new storage.

INFO: Waiting for '/test2' to be mounted...
INFO: Waiting for '/test' to be mounted...
INFO: Mount point '/test2' was mounted.
INFO: Mount point '/test' was mounted.

Filesystems were mounted.

Filesystem              Size  Used Avail Use% Mounted on
devtmpfs                8.3G     0  8.3G   0% /dev
tmpfs                   8.3G     0  8.3G   0% /dev/shm
tmpfs                   8.3G  8.9M  8.3G   1% /run
tmpfs                   8.3G     0  8.3G   0% /sys/fs/cgroup
/dev/sda2                54G   11G   44G  20% /
/dev/sda1               210M  6.1M  204M   3% /boot/efi
tmpfs                   1.7G     0  1.7G   0% /run/user/0
tmpfs                   1.7G     0  1.7G   0% /run/user/3672659445
10.137.60.82:/nfsshare  1.1T     0  1.1T   0% /test
10.45.3.250:/nfsshare   1.1T     0  1.1T   0% /test2