init: use Errorf() now that we have it

Init had some pretty horrid Error() << StringPrintf(...) calls that
are all much better replaced by Errorf(...) now.

Test: build, check that keyword_map errors look correct
Change-Id: I572588c7541b928c72ae1bf140b814acdef1cd60
diff --git a/init/result.h b/init/result.h
index 8c1f91e..b70dd1b 100644
--- a/init/result.h
+++ b/init/result.h
@@ -22,6 +22,8 @@
 #include <android-base/result.h>
 
 using android::base::ErrnoError;
+using android::base::ErrnoErrorf;
 using android::base::Error;
+using android::base::Errorf;
 using android::base::Result;
 using android::base::ResultError;