Tools: hv: kvp: ensure kvp device fd is closed on exec

KVP daemon does fork()/exec() (with popen()) so we need to close our fds
to avoid sharing them with child processes. The immediate implication of
not doing so I see is SELinux complaining about 'ip' trying to access
'/dev/vmbus/hv_kvp'.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>