The pid file can disappear when qemu is shutting down leading to a
file not found race before it is read.
Tweak the code to handle this and fix a rare but annoying race error
case.
[YOCTO #15036]
(From OE-Core rev: 8c07aac9d55f92fe5fbe3cab9f006efecf266328)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>