bluetoothHandler: fix segfault with early starting

This commit is trying to fix an early segfault.
If the bluetooth stack is not ready, then the `Powered` value is null.
Calling the `set_value` in this stage is causing `Segmentation fault`.

This was leading to problems with automatic AA start on the Pi,
so it was often necessary to start it manually afterwards:
`/etc/init.d/S93aawgd start` (the process was not running)

Author: manio

aa_wireless_dongle/package/aawg/src/bluetoothHandler.cpp

@@ -1,4 +1,5 @@
 #include <stdio.h>
+#include <unistd.h>
 
 #include "common.h"
 #include "bluetoothHandler.h"
@@ -99,6 +100,12 @@ void BluetoothHandler::setPower(bool on) {
         return;
     }
 
+    // wait up to 10 seconds if BT stack is not ready
+    int i = 10;
+    while (i-- && !m_adapter->powered->value()) {
+        sleep(1);
+    }
+
     m_adapter->powered->set_value(on);
     Logger::instance()->info("Bluetooth adapter was powered %s\n", on ? "on" : "off");
 }