Make apex.updatable default to true.

Update tests accordingly and add a new test case for this.

Bug: 180375550
Test: Treehugger
Change-Id: I835e189f4dae1e4bc79dce7bc59b7b9c7bd19fd9
diff --git a/apex/apex.go b/apex/apex.go
index a4bdc63..8f388c4 100644
--- a/apex/apex.go
+++ b/apex/apex.go
@@ -121,7 +121,7 @@
 	// Whether this APEX is considered updatable or not. When set to true, this will enforce
 	// additional rules for making sure that the APEX is truly updatable. To be updatable,
 	// min_sdk_version should be set as well. This will also disable the size optimizations like
-	// symlinking to the system libs. Default is false.
+	// symlinking to the system libs. Default is true.
 	Updatable *bool
 
 	// Whether this APEX is installable to one of the partitions like system, vendor, etc.
@@ -1232,7 +1232,7 @@
 
 // Implements android.ApexBudleDepsInfoIntf
 func (a *apexBundle) Updatable() bool {
-	return proptools.Bool(a.properties.Updatable)
+	return proptools.BoolDefault(a.properties.Updatable, true)
 }
 
 // getCertString returns the name of the cert that should be used to sign this APEX. This is