Revert "REGTEST: Enable reg tests with HEAD HTTP method usage."

Revert "REGTEST: Enable reg tests with HEAD HTTP method usage."

This reverts commit 47e4e13c0177b1cc910e1a62575a5e12235ba2c4.

It's a temporary revert. This commit suggested to update to vtest
commit 4e43cc1 to fix handling of HEAD requests, but the compression
was broken two commits before, leaving us with no single version of
vtest being able to run all tests anymore.

Let's temporary disable HEAD again in the tests so that we can use
any version up to and including a2e82a8 for the time it takes vtest
to fix the compression.