This reverts commit ac73682a.

This reverts commit 6620f803.

Previously, a completed file upload lead to this assert:
    Q_ASSERT(!_ackTimer.isActive());
because _closeUploadSeesion() was called twice, thus activating the timer
twice.

Plus other ui tweaks

Hide "Save Path" as it breaks the UI in General Settings.

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Helps battery life

PX4 Firmware plugin: First try to switch flight mode, then arm if successful - which is a lot safer than arming and then seeing if we can switch modes.

Firmwareplugin: Trim retry period to something that matches closer the users attention and is still long enough to allow for multiple heartbeats to pass through