runqemu-ifupdown/get-tapdevs: Add support for ip tuntap

runqemu-ifupdown/get-tapdevs: Add support for ip tuntap

The *ip* command supports the creation and destruction of TAP devices since
2009 and might be more likely installed on systems then *tunctl*. Therefore
it should be tried to setup or teardown the TAP interface with *ip* before
falling back to *tunctl*.

https://git.kernel.org/pub/scm/network/iproute2/iproute2.git/commit/?id=580fbd88f75cc9eea0d28a48c025b090eb9419a7

Signed-off-by: Jörg Sommer <joerg.sommer@navimatix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>