buildman: Move to absolute imports

At present buildman sets the python path on startup so that it can access
the libraries it needs. If we convert to use absolute imports this is not
necessary.

Move buildman to use absolute imports. Also adjust moveconfig.py too since
it uses some buildman modules and cannot work without this.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/buildman/func_test.py b/tools/buildman/func_test.py
index 29b28f5..9bfdd53 100644
--- a/tools/buildman/func_test.py
+++ b/tools/buildman/func_test.py
@@ -8,11 +8,12 @@
 import tempfile
 import unittest
 
-import board
-import bsettings
-import cmdline
+from buildman import board
+from buildman import bsettings
+from buildman import cmdline
+from buildman import control
+from buildman import toolchain
 import command
-import control
 import gitutil
 import terminal
 import toolchain