adb: add reconnect command.

Add reconnect command for debugging. `reconnect` kicks a transport
from the host side, `reconnect device` kicks a transport from
the device side. They can be used to produce transport errors.

Bug: 25935458

Change-Id: I47daa338796b561941e7aba44a51a6dd117d1e98
diff --git a/adb/adb.cpp b/adb/adb.cpp
index cb54d04..e0c0503 100644
--- a/adb/adb.cpp
+++ b/adb/adb.cpp
@@ -1134,6 +1134,13 @@
         /* we don't even need to send a reply */
         return 0;
     }
+
+    if (!strcmp(service, "reconnect")) {
+        if (s->transport != nullptr) {
+            kick_transport(s->transport);
+        }
+        return SendOkay(reply_fd, "done");
+    }
 #endif // ADB_HOST
 
     int ret = handle_forward_request(service, type, serial, reply_fd);