fixes weird drone health status

a non-damaged drone has 35 health and 35 maxHealth.
in the current proc, that is shown as (( 35 +35)/(35*2))*100 = 100 % health
a drone at half its health has 17.5 health.
current proc : (( 17.5 +35)/(35*2))*100 = 75 % health
a dead drone has 0 health.
current proc : ( 0 +35)/(35*2))*100 = 50 % health

as i fixed this proc in the silicon parent proc, this can be removed.
(cherry picked from commit 3bab559fc8f6160f0c5e20e8ac37f5e3473fb8c4)

Conflicts:
	code/modules/mob/living/silicon/robot/drone/drone.dm
Fixes bug with drone Bump() check

They can now use teleporters, hand tele portals and the disposals chute.
(cherry picked from commit 9401dcf13c9f062011e9308e665748e9b2ad9110)