If a terminal fails to spawn() we should continue looking.
gnome-terminal, in particular can be present but not start.
(From OE-Core rev: 6e4babdeee38d32002a4c9129e77466ae4156dd7)
Signed-off-by: Joe Slater <joe.slater@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>