Revert "adbd: switch the default USB implementation."

This reverts commit 12f328489b4642162a427c6d8d3b13af48ad825b.

Reason for revert: possibly causing b/126388431

Change-Id: Ida7c30a92f552f923f3bcb153d945d58ebbc4257
diff --git a/adb/daemon/usb.cpp b/adb/daemon/usb.cpp
index 69d1c31..f0e2861 100644
--- a/adb/daemon/usb.cpp
+++ b/adb/daemon/usb.cpp
@@ -628,10 +628,9 @@
 }
 
 void usb_init() {
-    bool use_nonblocking = android::base::GetBoolProperty("persist.adb.nonblocking_ffs", true);
-    if (use_nonblocking) {
-        std::thread(usb_ffs_open_thread).detach();
-    } else {
+    if (!android::base::GetBoolProperty("persist.adb.nonblocking_ffs", false)) {
         usb_init_legacy();
+    } else {
+        std::thread(usb_ffs_open_thread).detach();
     }
 }