Improve java_sdk_library handling of test_current

When building a library against sdk_version: system_current it uses the
system stubs of any java_sdk_library that it references. Previously,
when building against sdk_version: test_current this used the public
stubs of any java_sdk_library. This change causes it to use the
test stubs instead to be consistent with the handling of system and
public.

Bug: 148080325
Test: updated the test
      ran m nothing which failed as expected
	  fixed the code
	  ran m nothing again which succeeded
Change-Id: I58ec5bd243701c5a5c75664e2bb615ce7b2f2441
diff --git a/java/sdk_library.go b/java/sdk_library.go
index 0ef0f23..d51d317 100644
--- a/java/sdk_library.go
+++ b/java/sdk_library.go
@@ -689,16 +689,19 @@
 				return module.Library.ImplementationJars()
 			}
 		}
-		var paths *scopePaths
+		var apiScope *apiScope
 		switch sdkVersion.kind {
 		case sdkSystem:
-			paths = module.getScopePaths(apiScopeSystem)
+			apiScope = apiScopeSystem
+		case sdkTest:
+			apiScope = apiScopeTest
 		case sdkPrivate:
 			return module.Library.HeaderJars()
 		default:
-			paths = module.getScopePaths(apiScopePublic)
+			apiScope = apiScopePublic
 		}
 
+		paths := module.getScopePaths(apiScope)
 		if headerJars {
 			return paths.stubsHeaderPath
 		} else {