lp_battery_color: optimize colormap code when LP_PERCENT_ALWAYS=1

Better code (less comparisons) for colorization of the battery level
percent value.
Simplify % escape for zsh
hostname: fix LP_ENABLE_SSH_COLORS

Colorization of the hostname based on a hash of the name was broken for
some time because t_setaf was not available where LP_COLOR_SSH was used.