Add current clients to servicediscovery dumpsys

In addition to logs, add the list of current clients and their requests
to the servicediscovery dumpsys.

This is useful to know what is being queried at a given time, and to
monitor listener leaks (sometimes by apps).

Sample output:
Active clients:
  mUid 1000, mResolvedService null, mIsLegacy false, mUseJavaBackend \
      true, mClientRequests:
    2: Advertiser: serviceFullName=OpenThread BorderRouter \
            #850C._meshcop._udp, net=null \
        {2, startTime 18721, foundServices 0, lostServices \
	0, fromCache false, sentQueries 0}

  mUid 10108, mResolvedService null, mIsLegacy false, mUseJavaBackend \
      true, mClientRequests:
    16: Discovery/DiscoveryListener: \
        serviceType=_nmt227941123._tcp.local, net=null \
	{17, startTime 298263, foundServices 3, lostServices \
	3, fromCache false, sentQueries 18}
    24: Advertiser: \
        serviceFullName=NsdTest223067831._nmt295637688._tcp, net=122 \
        {25, startTime 301849, foundServices 0, lostServices 0, \
	fromCache false, sentQueries 0}
    25: Discovery/DiscoveryListener: \
        serviceType=_nmt295637688._tcp.local, net=122 \
	{26, startTime 302663, foundServices 0, lostServices \
	0, fromCache false, sentQueries 1}

Test: dumpsys servicediscovery
Change-Id: I19051911a2f47582c75a564e1eeb1825796656bf
1 file changed