Change default jar time to match ziptime

Ziptime uses Jan 01 2008, use the same in soong_zip and merge_zips.

Test: manual
Change-Id: Ie79a2e7864a5ed5a74833caec0a50c25a451859e
diff --git a/jar/jar.go b/jar/jar.go
index 08fa1ab..653e5ee 100644
--- a/jar/jar.go
+++ b/jar/jar.go
@@ -31,7 +31,7 @@
 	ModuleInfoClass = "module-info.class"
 )
 
-var DefaultTime = time.Date(2009, 1, 1, 0, 0, 0, 0, time.UTC)
+var DefaultTime = time.Date(2008, 1, 1, 0, 0, 0, 0, time.UTC)
 
 var MetaDirExtra = [2]byte{0xca, 0xfe}