lib/oe/lsb: prefer /etc/os-release for distribution data

lib/oe/lsb: prefer /etc/os-release for distribution data

os-release(5) is an increasingly standard source of operating system
identification and more likely to be present on modern OS deployments, i.e.
many container variants of common distros include os-release and not the
lsb_release tool.

Therefore we should favour parsing /etc/os-release in distro_identifier(),
try lsb_release when that fails and finally fall back on various distro
specific sources of OS identification.

(From OE-Core rev: fc4eddecddec68d03a985086fa32db40ad0c7bfc)

Signed-off-by: Joshua Lock <joshua.g.lock@intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>