fix LD Rotary buffer, now Average LD can be used with 3sec integration...

previous Avg Eff is calculated using :

AvgLD =  sum(Speed[ 0..n]) / Sum(sinkRate[0 .. n-1] )

with "n" number of second,  Speed and SinkRate in m/s
this is wrong.

now is calculated using :

AvgLD =  sum(Speed[0 .. n]) / Sum(sinkRate[0 .. n-1] )

with "n" number of second,  Speed and SinkRate in cm/s
Remove Warning inside LDRotaryBuffer.cpp when compiling without DEBUG_ROTARY flags
fix task requiered altitude from start.
disable debug mode for rotary buffer