[charging fallback] introduce charging fallback mode. Fixes JB#22320

Identify if we fell back to charging or it was a user conscious decision.
This helps us to know if we should set a mode if the device lock gets
unlocked or not.

Signed-off-by: Philippe De Swert <philippe.deswert@jollamobile.com>
[charging fallback] Keep fallback state internal

As other programs might rely on the charging state and it does not make
a difference to them we better do not change the behaviour towards them.
So we do not broadcast the fallback state, just charging state.

(Also clarify some comment)

Signed-off-by: Philippe De Swert <philippe.deswert@jollamobile.com>
[devicelock] No need to set dbus return value a second time

Regardless if things go bad or not, other programs will need to
process the dbus call that started the devicelock callback. So
no need to set it again. Saves a few cpu cycles :D

Signed-off-by: Philippe De Swert <philippe.deswert@jollamobile.com>
[devicelock] Fix bug related to secondary device lock check

Due to the secondary device lock check the mode was always undefined
and charging mode not correctly set. Luckily the kernel fallback
of the charging driver kicks in, which is why this went unnoticed.

Signed-off-by: Philippe De Swert <philippe.deswert@jollamobile.com>
Revert "[usb-moded] Do not pop-up ask dialog if charging mode was chosen before device locked up. Fixes: JB#13550"

This reverts commit 3d011a02241fd11199d378bbe05a2d8066dcfd97.

We do not need charge_mode_set anymore as we have now a completely
separate charger fallback mode.

Signed-off-by: Philippe De Swert <philippe.deswert@jollamobile.com>

Conflicts:
	src/usb_moded.c
Merge pull request #18 from nemomobile/22320

[usb] Make sure the dialog shows after unlocking the devicelock