runtime: update android time_now call

This was broken in https://golang.org/cl/36255

Change-Id: Ib23323a745a650ac51b0ead161076f97efe6d7b7
Reviewed-on: https://go-review.googlesource.com/36543
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/write_err_android.go

@@ -144,7 +144,7 @@ func writeLogdHeader() int {
 	//      hdr[3:7] sec unsigned uint32, little endian.
 	//      hdr[7:11] nsec unsigned uint32, little endian.
 	hdr[0] = 0 // LOG_ID_MAIN
-	sec, nsec := time_now()
+	sec, nsec := walltime()
 	packUint32(hdr[3:7], uint32(sec))
 	packUint32(hdr[7:11], uint32(nsec))