Skip bootloader when the config is set to skip

On SMLIGHT SLZB-06 devices in USB mode the skip bootloader sequence
causes the esp32 in these devices to reset.

While there is a config option to disable skip bootloader, it is not
hooked up.

Ensure that it is possible to disable skip bootloader.

zigpy_znp/api.py

@@ -734,7 +734,12 @@ async def connect(self, *, test_port=True) -> None:
             # prevent any data from being sent
             if test_port:
                 # The reset indication callback is sent when some sticks start up
-                self.capabilities = (await self._skip_bootloader()).Capabilities
+                if self._znp_config[conf.CONF_SKIP_BOOTLOADER]:
+                    self.capabilities = (await self._skip_bootloader()).Capabilities
+                else:
+                    self.capabilities = (
+                        await self.request(c.SYS.Ping.Req())
+                    ).Capabilities
 
                 # We need to know how structs are packed to deserialize frames correctly
                 await self.nvram.determine_alignment()