Tools: hv: kvp: configurable external scripts path

error when running hypervkvpd:
$ sudo ./hv_kvp_daemon -n

sh: hv_get_dns_info: command not found
sh: hv_get_dhcp_info: command not found
sh: hv_get_dns_info: command not found
sh: hv_get_dhcp_info: command not found

The external scripts are not installed in system path,
adding a configurable macro.

Signed-off-by: Alex Fluter <afluter@yandex.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>