storage: fix vstorage backend build
storage: fix vstorage backend build

Add headers with declarations of  geteuid/getegid
and virGetUserName/virGetGroupName.

Signed-off-by: Nikolay Shirokovskiy <7fa0e2698a05be944b362bdf5d7736c0162e16c9@virtuozzo.com>
Reviewed-by: Andrea Bolognani <3ada0bee826c753786fdbba72243dfba997094cf@redhat.com>

crobinso/libvirt,nertpinx/libvirt,jardasgit/libvirt,libvirt/libvirt,crobinso/libvirt,zippy2/libvirt,jardasgit/libvirt,jfehlig/libvirt,jardasgit/libvirt,libvirt/libvirt,nertpinx/libvirt,nertpinx/libvirt,olafhering/libvirt,crobinso/libvirt,jfehlig/libvirt,jardasgit/libvirt,zippy2/libvirt,olafhering/libvirt,jardasgit/libvirt,olafhering/libvirt,libvirt/libvirt,nertpinx/libvirt,libvirt/libvirt,jfehlig/libvirt,olafhering/libvirt,nertpinx/libvirt,zippy2/libvirt,crobinso/libvirt,zippy2/libvirt,jfehlig/libvirt