Add Mount RC failsafe handling

[peterbarker]

@Hwurzburg

[peterbarker]

Maybe s/in_rc_failsafe/in_failsafe/

[Hwurzburg]

want me to SITL and bench test this? and close mine?

[peterbarker]

want me to SITL and bench test this? and close mine?

Yes please!

[khancyr]

Looks good
It would be cool to write a small test for this too

[peterbarker]

On Fri, 8 Jan 2021, Pierre Kancir wrote: looks like we can merge the two cases

Read a little harder. They *look* very similar :-)

[peterbarker]

On Fri, 8 Jan 2021, Pierre Kancir wrote: looks like is miss some indent here

Yeah, I retained the original indent for no particularly good reason.

[khancyr]

One word : dyslexia ;-S

[peterbarker]

I tried the pure-virtual thing. It didn't work out. Too much stuff to be reverted when we move the failsafe handling up.

[Hwurzburg]

@peterbarker having a problem running SITL on this...if I use master/realfight griffin to get the mount, setting SIM_RC_FAIL puts it into failsafe...if I load this, it just disconnects RC from the controller box...maybe its a flightaxis thing...but cant test in STIL as is

[Hwurzburg]

btw, noticed that if I use RC mavproxy command it overrides the flight axis control box for that channel until I set RC X 0....probably should document...I assume it also does this in pure Mavproxy if joystick module is used?

[peterbarker]

Closes #24093

[rmackay9]

This looks OK to me although I wonder if we really need the extra parameter. I would have though just an MNTx_OPTION bit to move to Neutral on RC failsafe would have been enough.

[rmackay9]

We decided to use an option bit instead of adding the extra parameter, thanks!

[peterbarker]

Board                    AP_Periph  blimp  bootloader  copter  heli  iofirmware  plane  rover  sub
CubeOrange-periph-heavy  *                                                                     
CubeRedPrimary                      0      *           -256    -256              -256   -256   -256
Durandal                            *      *           -304    -304              -312   -304   -312
Hitec-Airspeed           *                                                                     
KakuteH7-bdshot                     *      *           -216    -216              -216   -216   -216
MatekF405                           *      *           *       *                 *      *      *
Pixhawk1-1M-bdshot                  *                  *       *                 *      *      *
f103-QiotekPeriph        *                                                                     
f303-Universal           *                                                                     
iomcu                                                                *                         
revo-mini                           *      *           *       *                 *      *      *
skyviper-journey                                       -112                                    
skyviper-v2450                                         *                                       

Fixed