libprocessgroup: Fix return values

We want our default implementations to fail, but '-1' is implicitly
cast to 'true', since it's non-zero.  We explicitly use 'false' to
fix this.

Test: TreeHugger
Change-Id: I369897b519601ce1a887cf6acd5f2cb9a6113a9a
diff --git a/libprocessgroup/task_profiles.h b/libprocessgroup/task_profiles.h
index 886ead1..83e74b2 100644
--- a/libprocessgroup/task_profiles.h
+++ b/libprocessgroup/task_profiles.h
@@ -46,8 +46,8 @@
     virtual ~ProfileAction() {}
 
     // Default implementations will fail
-    virtual bool ExecuteForProcess(uid_t, pid_t) const { return -1; };
-    virtual bool ExecuteForTask(int) const { return -1; };
+    virtual bool ExecuteForProcess(uid_t, pid_t) const { return false; };
+    virtual bool ExecuteForTask(int) const { return false; };
 };
 
 // Profile actions