[Autotest][Py3] Update common_lib/hosts/__init__ to have full imports

Updating relative imports to full imports in support of python3 migration

BUG=chromium:990593
TEST=dummy_Pass (python2 and 3)

Change-Id: I3febef9c479fa19aab2cfaa6e508620828ba3024
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/autotest/+/2546847
Tested-by: Derek Beckett <dbeckett@chromium.org>
Reviewed-by: Gregory Nisbet <gregorynisbet@google.com>
Commit-Queue: Derek Beckett <dbeckett@chromium.org>
diff --git a/client/common_lib/hosts/__init__.py b/client/common_lib/hosts/__init__.py
index 62c3ec9..1922143 100644
--- a/client/common_lib/hosts/__init__.py
+++ b/client/common_lib/hosts/__init__.py
@@ -7,5 +7,9 @@
 """
 
 from autotest_lib.client.common_lib import utils
-from base_classes import Host
-from repair import *
+try:
+    from autotest_lib.client.common_lib.hosts.base_classes import Host
+    from autotest_lib.client.common_lib.hosts.repair import *
+except ImportError:
+    from base_classes import Host
+    from repair import *