Move permission enforcement to onCommand

Calling enforceCallingOrSelfPermission in the shell command constructor
causes a hang when running GTS if the permission isn't granted.

Bug: 191043641
Test: Run "cmd contexthub deny" and verify error is printed if not rooted
Change-Id: I807adee4382310a201c34e31cd53fbb37574e851

services/core/java/com/android/server/location/contexthub/ContextHubShellCommand.java

@@ -32,16 +32,18 @@ public class ContextHubShellCommand extends ShellCommand {
 
     // Internal service impl -- must perform security checks before touching.
     private final ContextHubService mInternal;
+    private final Context mContext;
 
     public ContextHubShellCommand(Context context, ContextHubService service) {
         mInternal = service;
-
-        context.enforceCallingOrSelfPermission(
-                android.Manifest.permission.ACCESS_CONTEXT_HUB, "ContextHubShellCommand");
+        mContext = context;
     }
 
     @Override
     public int onCommand(String cmd) {
+        mContext.enforceCallingOrSelfPermission(
+                android.Manifest.permission.ACCESS_CONTEXT_HUB, "ContextHubShellCommand");
+
         if ("deny".equals(cmd)) {
             return runDisableAuth();
         }