Fix adb hang when subprocess dies early.

* Handling of the subprocess and its FD.
  This fixes http://b/3400254 "Many bugreports getting hung at the end in monkey"
  -  Start up a service thread that waits on the subprocess to terminate,
then closes the FD associated with it.
  -  Have the event handler select() with a timeout so that it can
  detect the closed FD. Select() with no timeout does not return when an FD is closed.
  - Have the event handler force a read on the closed FD to trigger the close sequence.
  - Migrate the "shell:blabla" handling to "#if !ADB_HOST" sections.
* Fix the race around OOM adjusting.
  - Do it in the child before exec() instead of the in the parent as the
   child could already have started or not (no /proc/pid/... yet).
* Allow for multi-threaded D() invocations to not clobber each other.
  - Allow locks across object files.
  - Add lock within D()
* Add some missing close(fd) calls
  - Match similar existing practices near dup2()
* Add extra D() invocations related to FD handling.
* Warn about using debugging as stderr/stdout is used for protocol.

Change-Id: Ie5c4a5e6bfbe3f22201adf5f9a205d32e069bf9d
Signed-off-by: JP Abgrall <jpa@google.com>
diff --git a/adb/adb_client.c b/adb/adb_client.c
index 882810a..9a812f0 100644
--- a/adb/adb_client.c
+++ b/adb/adb_client.c
@@ -202,6 +202,7 @@
         return -1;
     }
 
+    D("_adb_connect: return fd %d\n", fd);
     return fd;
 }
 
@@ -210,6 +211,7 @@
     // first query the adb server's version
     int fd = _adb_connect("host:version");
 
+    D("adb_connect: service %s\n", service);
     if(fd == -2) {
         fprintf(stdout,"* daemon not running. starting it now on port %d *\n",
                 __adb_server_port);
@@ -266,6 +268,7 @@
     if(fd == -2) {
         fprintf(stderr,"** daemon still not running");
     }
+    D("adb_connect: return fd %d\n", fd);
 
     return fd;
 error: