render_mem_usage_percent() treated any value above 1 as a byte count
and recalculated the percentage from 'mem' and 'maxmem'. But the memory
usage ratio of a guest can legitimately exceed 1, for example when the
reported usage is the host-side memory of the QEMU process, which
includes its own overhead. In the reported case, 'mem' was 2222472192
with a 'maxmem' of 2147483648, so the ratio of about 1.035 got taken as
bytes and the search and resource grids showed 0.0 % instead of 103.5 %.
All users of the renderer now pass the usage as a ratio, so drop the
bytes fallback and always render the value as percentage.
Signed-off-by: Michal Fox <me@dualfroz.com>