Use IApexService.stagePackages instead of stagePackage

IApexService.stagePackage is going away (see another CL in this topic).

Bug: 136078302
Test: builds
Change-Id: I0552b4c514b921163d4737304483b39adf834897
Merged-In: If0bd3d368c7373ab0028211a8a4246a9821893af
diff --git a/services/core/java/com/android/server/pm/PackageInstallerSession.java b/services/core/java/com/android/server/pm/PackageInstallerSession.java
index 57deb3f..fa570b8 100644
--- a/services/core/java/com/android/server/pm/PackageInstallerSession.java
+++ b/services/core/java/com/android/server/pm/PackageInstallerSession.java
@@ -115,6 +115,7 @@
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -959,7 +960,7 @@
         try {
             IApexService apex = IApexService.Stub.asInterface(
                     ServiceManager.getService("apexservice"));
-            apex.stagePackage(mResolvedBaseFile.toString());
+            apex.stagePackages(Collections.singletonList(mResolvedBaseFile.toString()));
         } catch (Throwable e) {
             // Convert all exceptions into package manager exceptions as only those are handled
             // in the code above