adb: fix output of `sync -l`

sync with list-only was using SyncConnection::Error to print its output
persistently, which would prepend "adb: error: " to messages.

Change-Id: I90df5fc1123b8c613c811cf66c37aef05663b1e4
diff --git a/file_sync_client.cpp b/file_sync_client.cpp
index fbca770..454de41 100644
--- a/file_sync_client.cpp
+++ b/file_sync_client.cpp
@@ -699,7 +699,7 @@
     for (const copyinfo& ci : file_list) {
         if (!ci.skip) {
             if (list_only) {
-                sc.Error("would push: %s -> %s", ci.lpath.c_str(), ci.rpath.c_str());
+                sc.Println("would push: %s -> %s", ci.lpath.c_str(), ci.rpath.c_str());
             } else {
                 if (!sync_send(sc, ci.lpath.c_str(), ci.rpath.c_str(), ci.time, ci.mode)) {
                     return false;