Add the feature to execute shell commands on each wpa_supplicant/hostapd
interface host. When executing remote tests the interfaces are not all
on a single host so when executing shell commands the test needs to
execute the command on the host which the interface relevant for the
command is on. This patch enables tests to execute the command on the
relevant host.
Signed-off-by: Jonathan Afek <jonathanx.afek@intel.com>