[autotest] Delete code for creating Android testbeds.

This deletes all factory code creating testbed.TestBed instances,
along with some related external references to the TestBed class.

BUG=chromium:834335
TEST=TBD

Change-Id: Ie400c0c6a1d13aa01130dd38b71b45b0809a2476
Reviewed-on: https://chromium-review.googlesource.com/1029353
Commit-Ready: Richard Barnette <jrbarnette@chromium.org>
Tested-by: Richard Barnette <jrbarnette@chromium.org>
Reviewed-by: Aviv Keshet <akeshet@chromium.org>
diff --git a/server/site_utils.py b/server/site_utils.py
index 51cede7..95579d5 100644
--- a/server/site_utils.py
+++ b/server/site_utils.py
@@ -764,20 +764,6 @@
     return os.path.join(creds_dir, creds_file)
 
 
-def machine_is_testbed(machine):
-    """Checks if the machine is a testbed.
-
-    The signal we use to determine if the machine is a testbed
-    is if the host attributes contain more than 1 serial.
-
-    @param machine: is a list of dicts
-
-    @return: True if the machine is a testbed, False otherwise.
-    """
-    _, afe_host = get_host_info_from_machine(machine)
-    return len(afe_host.attributes.get('serials', '').split(',')) > 1
-
-
 def SetupTsMonGlobalState(*args, **kwargs):
     """Import-safe wrap around chromite.lib.ts_mon_config's setup function.
 
@@ -990,4 +976,4 @@
 
     _report_result_size_metrics(result_size_info)
 
-    return result_size_info
\ No newline at end of file
+    return result_size_info