OMS: dump: silently ignore -a

dumpsys will pass -a to each service. Teach the overlay manager to
silently ignore the argument.

Test: adb shell dumpsys | grep --text -A1 -e 'DUMP OF SERVICE overlay:' # no "Unknown argument: -a"
Change-Id: I00a786a8a3cd5996bfac95e05782b2f204f005c5
diff --git a/services/core/java/com/android/server/om/OverlayManagerService.java b/services/core/java/com/android/server/om/OverlayManagerService.java
index 8ecc607..5544669 100644
--- a/services/core/java/com/android/server/om/OverlayManagerService.java
+++ b/services/core/java/com/android/server/om/OverlayManagerService.java
@@ -1009,7 +1009,9 @@
                 }
                 opti++;
 
-                if ("-h".equals(opt)) {
+                if ("-a".equals(opt)) {
+                    // dumpsys will pass in -a; silently ignore it
+                } else if ("-h".equals(opt)) {
                     pw.println("dump [-h] [--verbose] [--user USER_ID] [[FIELD] PACKAGE]");
                     pw.println("  Print debugging information about the overlay manager.");
                     pw.println("  With optional parameter PACKAGE, limit output to the specified");