Fix the sense of a test in "adb sideload".

Change-Id: I516a2ad2d74d9322ff9eb2e4cd3c3829e5cbda99
diff --git a/adb/commandline.cpp b/adb/commandline.cpp
index 82fa19a..b815fef 100644
--- a/adb/commandline.cpp
+++ b/adb/commandline.cpp
@@ -889,7 +889,7 @@
             android::base::StringPrintf("sideload-host:%d:%d", sz, SIDELOAD_HOST_BLOCK_SIZE);
     std::string error;
     unique_fd fd(adb_connect(service, &error));
-    if (fd >= 0) {
+    if (fd < 0) {
         // Try falling back to the older sideload method.  Maybe this
         // is an older device that doesn't support sideload-host.
         printf("\n");