Plane: Fix MAV_CMD_NAV_LOITER_TURNS with zero turns skipping waypoint location

[joshanne]

In the case where MAV_CMD_NAV_LOITER_TURNS waypoint is used the AV can skip travelling to the waypoint and jump directly to the next waypoint (if the conditions are correct).

This ensures loiter turns cannot be verified as complete until both loiter target is reached and turn count is met (the latter half is unchanged).

First commit shows the issue occurring, and is an example use case where you might use 0-turn loiters.
Second commit shows the fix to the issue.

Before	After

[joshanne]

@peterbarker @tridge I suspect a similar issue of short circuiting a waypoint can occur with LOITER_TO_ALT, given it is not checking for reaching of the loiter target either.

[joshanne]

@peterbarker @tridge I suspect a similar issue of short circuiting a waypoint can occur with LOITER_TO_ALT, given it is not checking for reaching of the loiter target either.

Although, i haven't been able to prove this through a separate autotest.