examples/ubuntu/avahi_client: remove avahi-daemon startup logic

the daemon now expects that the avahi-daemon is running and print a
connection message.

Bug: 24268532

"""
PING talk.l.google.com (74.125.25.125) 56(84) bytes of data.
64 bytes from pa-in-f125.1e100.net (74.125.25.125): icmp_seq=1 ttl=50 time=20.9 ms

--- talk.l.google.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 20.967/20.967/20.967/0.000 ms
[0925/135340:INFO:avahi_client.cc(30)] connecting to avahi-daemon
[0925/135402:FATAL:avahi_client.cc(34)] Check failed: client_. Daemon not running
Aborted (core dumped)

real	0m22.700s
user	0m0.026s
sys	0m0.029s
""

I couldn't find a way to specify the connection timeout, maybe this
could be done by customizing the AvahiPoll looper (see bug 24408822).

Change-Id: I2704736cfc1ccc0de34c39785d146ac316edee60
Reviewed-on: https://weave-review.googlesource.com/1170
Reviewed-by: Vitaly Buka <vitalybuka@google.com>

libweave/examples/ubuntu/avahi_client.cc

diff --git a/libweave/examples/ubuntu/avahi_client.cc b/libweave/examples/ubuntu/avahi_client.cc
index 58d11d0..9c8cc0d 100644
--- a/libweave/examples/ubuntu/avahi_client.cc
+++ b/libweave/examples/ubuntu/avahi_client.cc
@@ -24,11 +24,10 @@
 }  // namespace
 
 AvahiClient::AvahiClient() {
-  CHECK_EQ(0, std::system("service avahi-daemon status | grep running || "
-                          "service avahi-daemon start"));
   thread_pool_.reset(avahi_threaded_poll_new());
   CHECK(thread_pool_);
 
+  LOG(INFO) << "connecting to avahi-daemon";
   int ret = 0;
   client_.reset(avahi_client_new(avahi_threaded_poll_get(thread_pool_.get()),
                                  {}, nullptr, this, &ret));