Clear Shill stub config in offline file manager tests

The Shill stub client fakes ethernet and wifi connections during
testing. Clear its config during offline tests to simulate a lack of
network connectivity.

As a side effect, fileManagerPrivate.getDriveConnectionState will no
longer need to be stubbed out, as it will now think the device is
offline and return the appropriate result.

Bug: 925272
Change-Id: Idd6cb44325cfde4991d3b1e64185a28e8655c733
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1578149
Commit-Queue: Austin Tankiang <austinct@chromium.org>
Reviewed-by: Sam McNally <sammc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#654782}
  bool PrepareDcimTestEntries(Profile* profile) {
    if (!CreateRootDirectory(profile))
      return false;

    CreateEntry(AddEntriesMessage::TestEntryInfo(AddEntriesMessage::DIRECTORY,
                                                 "", "DCIM"));
    CreateEntry(AddEntriesMessage::TestEntryInfo(AddEntriesMessage::FILE,
                                                 "image2.png", "image2.png")
                    .SetMimeType("image/png"));
    CreateEntry(AddEntriesMessage::TestEntryInfo(
                    AddEntriesMessage::FILE, "image3.jpg", "DCIM/image3.jpg")
                    .SetMimeType("image/png"));
    CreateEntry(AddEntriesMessage::TestEntryInfo(AddEntriesMessage::FILE,
                                                 "text.txt", "DCIM/hello.txt")
                    .SetMimeType("text/plain"));
    base::RunLoop().RunUntilIdle();
    return true;
  }

  bool PrepareDcimTestEntries(Profile* profile) {
    if (!CreateRootDirectory(profile))
      return false;

    CreateEntry(AddEntriesMessage::TestEntryInfo(AddEntriesMessage::DIRECTORY,
                                                 "", "DCIM"));
    CreateEntry(AddEntriesMessage::TestEntryInfo(AddEntriesMessage::FILE,
                                                 "image2.png", "image2.png")
                    .SetMimeType("image/png"));
    CreateEntry(AddEntriesMessage::TestEntryInfo(
                    AddEntriesMessage::FILE, "image3.jpg", "DCIM/image3.jpg")
                    .SetMimeType("image/png"));
    CreateEntry(AddEntriesMessage::TestEntryInfo(AddEntriesMessage::FILE,
                                                 "text.txt", "DCIM/hello.txt")
                    .SetMimeType("text/plain"));
    base::RunLoop().RunUntilIdle();
    return true;
  }
