Fix SettingsXml start tag logic

Don't move to next tag if the current tag is the START_TAG. The initial
implementation assumed domain verification state would write to a new
XML file, but it ended up being stuffed into packages.xml, so the
start tag is already read in the initial switch that calls into
DomainVerificationService.

Bug: 180527086

Test: atest DomainVerificationPersistenceTest

Change-Id: I623afb08985bf5377cb9ae240805aae5db9cd820

services/core/java/com/android/server/pm/SettingsXml.java

@@ -181,7 +181,10 @@ public class SettingsXml {
         }
 
         private void moveToFirstTag() throws IOException, XmlPullParserException {
-            // Move to first tag
+            if (mParser.getEventType() == XmlPullParser.START_TAG) {
+                return;
+            }
+
             int type;
             //noinspection StatementWithEmptyBody
             while ((type = mParser.next()) != XmlPullParser.START_TAG