Harden NsdManager against null-dereference crashes

Due to race conditions or programming errors, the NsdManager
can attempt to process an asynchronous status message (and issue
a callback to the listener) after the listener has already been
removed from the NsdManager state.  This causes dereferencing of
null objects, and a crash.

Split out the three async-queue message cases:  these are ones
in which message.arg2 does not hold an NsdManager array index
and the code should not interpret this field as if it were.

Add an explicit check for "null listener" (the array index in the
message has already been released), log a warning, and exit early.

Safeguard accesses to the "NSD service type" string from a (possibly
null) NsdServiceInfo object... return a constant "?" string rather
than crashing.

Bug: 9016259

Change-Id: I40aabdfc65d86fdd0eaac7a1e7e56e6ff69796cf
Validate objects are from the correct context.

Change-Id: I7d87b0e253b8d2e36d1aed790cfe3a7dd23e158f
Fix descriptor leak after accepting connections

After accepting a connection on a listening socket and
storing the resulting FileDescriptor into a newly created
LocalSocketImpl, the new impl's "descriptor was created
locally and should be closed normally" flag should be set.

(cherrypicked from 3e7305c6bf6062b5cb1e2ddcec6c6d30b4a8bc0d)

Bug: 11805817
Change-Id: I0a1a7c62ec3fbcf647a44a22110ddc778d14e5f4