dbus: Suppress NameHasNoOwner errors when connecting to signals

dbus: Suppress NameHasNoOwner errors when connecting to signals

The NameHasNoOwner errors are emitted as Chrome tries to get the
identity of the service when connecting to signals for sender
verification (crbug.com/140938), but the service may not yet be
running, which is all right, hence the NameHasNoOwner errors here
should be just supressed.

BUG=273829
TEST=out/Debug/dbus_unittests --gtest_filter=SignalSenderVerificationTest.TestSignalAccepted; confirm that NameHasNoOwner is no longre emitted. Previously, an error message like below was emited:

[12721:12722:0816/144031:3991948732792:ERROR:bus.cc(892)] Failed to get name owner. Got org.freedesktop.DBus.Error.NameHasNoOwner: Could not get owner of name 'org.chromium.TestService': no such name

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=217980

[Seigo Nonaka, 2013-08-16 07:05:12]

lgtm

[commit-bot: I haz the power, 2013-08-16 07:05:54]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/satorux@chromium.org/23143004/1

[commit-bot: I haz the power, 2013-08-16 09:16:43]

Change committed as 217980