adb: switch the socket list mutex to a recursive_mutex.

sockets.cpp was branching on whether a socket close function was
local_socket_close in order to avoid a potential deadlock if the socket
list lock was held while closing a peer socket.

Bug: http://b/28347842
Change-Id: I5e56f17fa54275284787f0f1dc150d1960256ab3
(cherry picked from commit 9b587dec6d0a57c8fe1083c1c543fbeb163d65fa)

static void local_socket_close(asocket* s) {

static void local_socket_close(asocket* s) {
    adb_mutex_lock(&socket_list_lock);
    local_socket_close_locked(s);
    adb_mutex_unlock(&socket_list_lock);
}
