anthos-bm-gcp-bash failing to complete due to lack of permissions

Today, ssh'ing into GCE machines resorts to using OS Login user instead of `root`, meaning that operations on the VMs requiring root permissions will fail:

```text
Setting up VxLAN in the GCE VMs...
Using OS Login user [student-04-bcdd0236eaea] instead of requested user [root]
[...]
E: Could not open lock file /var/lib/apt/lists/lock - open (13: Permission denied)
E: Unable to lock directory /var/lib/apt/lists/
W: Problem unlinking the file /var/cache/apt/pkgcache.bin - RemoveCaches (13: Permission denied)
W: Problem unlinking the file /var/cache/apt/srcpkgcache.bin - RemoveCaches (13: Permission denied)
E: Could not open lock file /var/lib/dpkg/lock-frontend - open (13: Permission denied)
E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), are you root?
+ ip link add vxlan0 type vxlan id 42 dev ens4 dstport 0
RTNETLINK answers: Operation not permitted
[...]
```

All operations trying to log into the GCE machines as root in the `install_hybrind_cluster.sh` script need to be changed so the user elevates to root permissions, for example doing a `sudo su -` as a first step.