Gem5Device: Move resize shell commands to own method

Moved the commands to resize the shell to their own method. They are
now executed twice. Once as soon as the shell is connected, and a
second time as part of initialize. This latter call takes place after
the isntallation of busybox.

wlauto/devices/linux/gem5/__init__.py

@@ -108,3 +108,6 @@ class Gem5LinuxDevice(BaseGem5Device, LinuxDevice):
         # If we didn't manage to do the above, call the parent class.
         self.logger.warning("capture_screen: falling back to parent class implementation")
         LinuxDevice.capture_screen(self, filepath)
+
+    def initialize(self, context):
+        self.resize_shell()