shill: Allow creation and push of DefaultProfile

Add the ability to create a DefaultProfile whose name is not
"default".  Add the ability to push a DefaultProfile atop
another DefaultProfile in the Manager.  This will enable
autotests to run that can test interactions between profiles
while a user is not logged in.

BUG=chromium-os:24461
TEST=New unit tests; autotests to come

Change-Id: Iccfcff6ec613cf0a8ac55c11c9cc1efac8237807
Reviewed-on: https://gerrit.chromium.org/gerrit/19287
Reviewed-by: Paul Stewart <pstew@chromium.org>
Tested-by: Paul Stewart <pstew@chromium.org>
Commit-Ready: Paul Stewart <pstew@chromium.org>
diff --git a/default_profile_unittest.cc b/default_profile_unittest.cc
index c49beb4..301dfd4 100644
--- a/default_profile_unittest.cc
+++ b/default_profile_unittest.cc
@@ -38,6 +38,7 @@
       : profile_(new DefaultProfile(control_interface(),
                                     manager(),
                                     FilePath(storage_path()),
+                                    DefaultProfile::kDefaultId,
                                     properties_)),
         device_(new MockDevice(control_interface(),
                                dispatcher(),