BQLmon: remove has_colors() check

Even though the terminal does not support colors, there is no reason why
we should exit, as ncurses is smart enough to produce a good black and
white rendering anyway.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
BQLmon: free ctx->queues on exit

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
BQLmon: fix queue display with small terminals

The x_end - x_start comparison would be false too early, make sure we
use vq_end as the upper limit since it is correctly bounded.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>