scsi/qemu-pr-helper: Drop support for 'old' libmultipath API

scsi/qemu-pr-helper: Drop support for 'old' libmultipath API

Commit 1b0578f5c4 ("qemu-pr-helper: Fix build on CentOS 7") added
code to probe for 'old' libmultipath API on CentOS 7. However since
merge commit 8c345b3e6a (June 2021) we don't build/test CentOS 7 as
it felt out of our list of supported distrib versions. Therefore we
can safely remove the 'old' API check (mostly reverting commit
1b0578f5c4, except the code got converted to meson in commit
6ec0e15d95 "meson: move libmpathpersist test").

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20230605174146.87440-2-philmd@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>