vio: Fix compile error if WITH_UNIT_TESTING is not defined.
vio: Fix compile error if WITH_UNIT_TESTING is not defined.

Reviewed-by: Andreas Schneider <5be00ddc76278cf6077f5047ca3384a88460c671@cryptomilk.org>

gco/csync,meeh420/csync,gco/csync,gco/csync,meeh420/csync,meeh420/csync,gco/csync