We now spend time copying the VM image into a tmpfs and with IO load on the
system, the time + the boot time of the VM can take longer than 120s. Increase
the timeout to match the added overhead of copying the image file.
(From OE-Core rev: a40087c966af5ffb9309e1ddfdb3d06973e0bddd)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>