recovery: move log output to stdout

Recovery currently has a random mix of messages printed to stdout and
messages printed to stderr, which can make logs hard to read.  Move
everything to stdout.

Change-Id: Ie33bd4a9e1272e731302569cdec918e0534c48a6
diff --git a/install.cpp b/install.cpp
index 0cb5cc7..e1ab848 100644
--- a/install.cpp
+++ b/install.cpp
@@ -154,6 +154,7 @@
             } else {
                 ui->Print("\n");
             }
+            fflush(stdout);
         } else if (strcmp(command, "wipe_cache") == 0) {
             *wipe_cache = 1;
         } else if (strcmp(command, "clear_display") == 0) {