Use --disable= in subscription-manager to avoid shell expansion.

Use --disable= in subscription-manager to avoid shell expansion.

In extraconfig/pre_deploy/rhel-registration/scripts/rhel-registration,
there's a line that says:

   retry subscription-manager repos --disable '*'

I believe this is broken and will result in shell expansion being made.
The proper line should be:

   retry subscription-manager repos --disable='*'

This regression came from commit 2b06ed8adce2bcc18480b71c0f20a0ec2d21de19.
(Also see https://review.openstack.org/#/c/381233 )

This patch fixes the regression while preserving functionality
of the above change.

Closes-Bug: 1667316

Change-Id: I54f0db3f1f596f6356f7445cdc61737f20f14318
Signed-off-by: Vincent S. Cojot <vincent@cojot.name>
(cherry picked from commit 87569bd5711eaf79c1a3f0a4449daef860626daa)