runqemu: work even if a *.qemuboot.conf isn't found
A qemuboot conf file is a convenience but it should still be
possible to invoke runqemu without them, especially for examples
such as using the SDK with an extracted rootfs via NFS.
As read_qemuboot() is always called we need to be sure that function
can return cleanly, without throwing Exceptions, even if a qemuboot
conf file isn't found.
Signed-off-by: Joshua Lock <joshua.g.lock@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
