security_selinux: Implement virSecurityManager{Set,Restore}SavedStateLabel
security_selinux: Implement virSecurityManager{Set,Restore}SavedStateLabel

These APIs are are basically
virSecuritySELinuxDomainSetPathLabelRO() and
virSecuritySELinuxDomainRestorePathLabel().

Signed-off-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>
Reviewed-by: Erik Skultety <2c14d38fa47c8799f1b9c16280abe27f8edfec6e@redhat.com>

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