init: allow services to have no capabilities set

In particular, this allows services running as the root user to have
capabilities removed instead of always having full capabilities.

Test: boot device with a root service with an empty capabilities
      option in init showing no capabilities in /proc/<pid>/status
Change-Id: I569a5573ed4bc5fab0eb37ce9224ab708e980451
diff --git a/init/service_test.cpp b/init/service_test.cpp
index 194aa2b..4bfaa6b 100644
--- a/init/service_test.cpp
+++ b/init/service_test.cpp
@@ -57,7 +57,7 @@
     }
 
     Service* service_in_old_memory2 = new (old_memory) Service(
-        "test_old_memory", 0U, 0U, 0U, std::vector<gid_t>(), CapSet(), 0U, "", nullptr, dummy_args);
+            "test_old_memory", 0U, 0U, 0U, std::vector<gid_t>(), 0U, "", nullptr, dummy_args);
 
     EXPECT_EQ(0U, service_in_old_memory2->flags());
     EXPECT_EQ(0, service_in_old_memory2->pid());