vstorage: remove build time checks for runtime binaries

vstorage: remove build time checks for runtime binaries

Accoring to current agreement mentioned in list recently [1]. Now
vstorage driver will be build in default devs environment and also can
be included into CI. This also closes quite old abandoned thread on
alternative checks for binaries in case of this same driver [2].

[1] https://www.redhat.com/archives/libvir-list/2021-January/msg00750.html
[2] https://www.redhat.com/archives/libvir-list/2020-July/msg00697.html

Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy@virtuozzo.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>