apiserver: use direct paths for ephemeral storage

[yeazelm]

Issue number:

Closes # bottlerocket-os/bottlerocket#4181

Description of changes:
The path for ephemeral storage devices is created by udev on early boot after ephemeral-storage init is called but if you call ephemeral-storage bind immediately after this, the path may not exist, causing the resulting commands to fail. This commit switches to a path that is known to exist to avoid this issue.

Testing done:
Tested on no, single, and multi-device Instance store EC2 instance types to confirm that when used with bootstrap-commands, they no longer exhibit the error.
From a booted instance:

# journalctl -D /.bottlerocket/rootfs/var/log/journal/ -u bootstrap-commands
localhost systemd[1]: Starting Bootstrap Commands...
localhost bootstrap-commands[6281]: 22:42:47 [INFO] Processing bootstrap command '000-test-bootstrap-commands' ...
internal bootstrap-commands[6281]: 22:42:48 [INFO] Turning off bootstrap command '000-test-bootstrap-commands'
internal bootstrap-commands[6281]: 22:42:48 [INFO] Successfully ran bootstrap command '000-test-bootstrap-commands'
internal systemd[1]: Finished Bootstrap Commands.

root@admin]# sheltie
bash-5.1# mount | grep md
ramfs on /run/credentials/systemd-sysusers.service type ramfs (ro,nosuid,nodev,noexec,relatime,mode=700)
ramfs on /run/credentials/systemd-tmpfiles-setup-dev.service type ramfs (ro,nosuid,nodev,noexec,relatime,mode=700)
ramfs on /run/credentials/systemd-sysctl.service type ramfs (ro,nosuid,nodev,noexec,relatime,mode=700)
ramfs on /run/credentials/systemd-tmpfiles-setup.service type ramfs (ro,nosuid,nodev,noexec,relatime,mode=700)
/dev/md127 on /mnt/.ephemeral type xfs (rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=256k,sunit=512,swidth=1024,noquota)
/dev/md127 on /var/lib/containerd type xfs (rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=256k,sunit=512,swidth=1024,noquota)
/dev/md127 on /var/lib/kubelet type xfs (rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=256k,sunit=512,swidth=1024,noquota)
/dev/md127 on /var/log/pods type xfs (rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=256k,sunit=512,swidth=1024,noquota)

Terms of contribution:

By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.

[yeazelm]

I found an issue with reboots, this method won't find the device after the reboot so we need a way to find this after the fact.

[yeazelm]

^ Added --homehost=any to the create commands to force the behavior needed for the array to come back after reboot.

[yeazelm]

^ Updated the labeling to be ephemeral for the filesystem.