adb: fix killing of old version of adb process

The original code was:

  if (strcmp(__adb_error, "unknown host service") != 0)

But that was changed by 04a98c2affb9f4a2b5baf79418793d0e6ba8d766 to:

  if (*error == "unknown host service") {

I think the comparison should be != so that "unknown host service"
falls-through and kills the server, and so if it is some other error,
that the other error is returned immediately.

Change-Id: Ia490a4a870d1d123a3c5ab258dd5fa0930e8032d
Signed-off-by: Spencer Low <CompareAndSwap@gmail.com>
diff --git a/adb_client.cpp b/adb_client.cpp
index 6d75966..afff2ef 100644
--- a/adb_client.cpp
+++ b/adb_client.cpp
@@ -229,8 +229,9 @@
             }
         } else {
             // if fd is -1, then check for "unknown host service",
-            // which would indicate a version of adb that does not support the version command
-            if (*error == "unknown host service") {
+            // which would indicate a version of adb that does not support the
+            // version command, in which case we should fall-through to kill it.
+            if (*error != "unknown host service") {
                 return fd;
             }
         }