This is required when the possible range of NetIds is large to
prevent netd consuming excessive amounts of memory.
This required replacing the per-cache locks in favor of a single
global lock to prevent accesses to deleted caches.
Change-Id: I99d058bafea5de743e56075dbed74031da4df63f
Replace iface cache key with netid.
Replace _mark with netid.
Mark sockets used to test IPv4/IPv6 support as well as sockets
used to determine source address for rfc6724 sort.
Remove pid/uid mappings (functionality moved to system/netd).
Do not create resolv_cache when it does not exist, but rather only
when DNS configuration is supplied.
Clean up unused functions.
Change-Id: I9ccfda2902cc0943e87c9bc346ad9a2578accdab
