Tools: hv: check return value of system in hv_kvp_daemon

hv_kvp_daemon.c: In function 'main':
hv_kvp_daemon.c:1441:8: warning: ignoring return value of 'daemon', declared with attribute warn_unused_result [-Wunused-result]

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>