[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/cli/host.py b/cli/host.py
index 3d8e161..05b152f 100644
--- a/cli/host.py
+++ b/cli/host.py
@@ -666,13 +666,9 @@
         try:
             if bin_utils.ping(host, tries=1, deadline=1) == 0:
                 serials = self.attributes.get('serials', '').split(',')
-                if serials and len(serials) > 1:
-                    host_dut = hosts.create_testbed(machine,
-                                                    adb_serials=serials)
-                else:
-                    adb_serial = self.attributes.get('serials')
-                    host_dut = hosts.create_host(machine,
-                                                 adb_serial=adb_serial)
+                adb_serial = self.attributes.get('serials')
+                host_dut = hosts.create_host(machine,
+                                             adb_serial=adb_serial)
 
                 info = HostInfo(host, host_dut.get_platform(),
                                 host_dut.get_labels())