DAOS-18606 control: Avoid NVMe driver unbind in VMD if blocklisted

[tanabarr]

When VMD is enabled, DAOS server first unbinds VMD-backing devices from
all drivers (DRIVER_OVERRIDE=none in SPDK setup script). This way the
subsequent binding process to userspace is quicker (see related
spdk/spdk#2926). If a PCI_BLOCKED env is
supplied then the backing devices behind the VMD addresses specified
in the env value are also unbound. This makes the server config file
bdev_exclude parameter ineffective and so as a workaround, the unbind
of all drivers is skipped when VMD is enabled and bdev_exclude is set.

Steps for the author:

• Commit message follows the guidelines.
• Appropriate Features or Test-tag pragmas were used.
• Appropriate Functional Test Stages were run.
• At least two positive code reviews including at least one code owner from each category referenced in the PR.
• Testing is complete. If necessary, forced-landing label added and a reason added in a comment.

After all prior steps are complete:

• Gatekeeper requested (daos-gatekeeper added as a reviewer).

[github-actions]

Ticket title is 'Not possible to use bdev_exclude with VMD enabled'
Status is 'Open'
Labels: 'VMD,md_on_ssd'
https://daosio.atlassian.net/browse/DAOS-18606

[daosbuild3]

Test stage Functional on EL 8.8 completed with status FAILURE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net//job/daos-stack/job/daos/view/change-requests/job/PR-17612/2/execution/node/1048/log