test: Python import cleanup

Some test scripts use "from gi.repository import GObject" whereas others
use "import gobject". gi.repository is not always available on embedded
systems, so convert all instances to this format:

try:
  from gi.repository import GObject
except ImportError:
  import gobject as GObject

Also, sort the imports in this order: system, dbus, gobject, bluezutils
diff --git a/test/test-hfp b/test/test-hfp
index 873de0a..a806043 100755
--- a/test/test-hfp
+++ b/test/test-hfp
@@ -2,16 +2,18 @@
 
 from __future__ import absolute_import, print_function, unicode_literals
 
-from gi.repository import GObject
-
+from optparse import OptionParser, make_option
 import os
+from socket import SOCK_SEQPACKET, socket
 import sys
 import dbus
-import glib
 import dbus.service
 import dbus.mainloop.glib
-from optparse import OptionParser, make_option
-from socket import SOCK_SEQPACKET, socket
+import glib
+try:
+  from gi.repository import GObject
+except ImportError:
+  import gobject as GObject
 
 mainloop = None
 audio_supported = True