Revert "CA-114341: check return value of LVHD plugins"

This reverts commit 4bdb01aa761d73519c2e14410a3e63f291918524. We revert
the commit because it uncovers an existing bug (fixing it is not
trivial) in order to unblock the merge.

Signed-off-by: Thanos Makatos <thanos.makatos@citrix.com>