Only run GentleKill test as root

Without root, Service::Start() fails due to lack of permissions.

Bug: 267559075
Test: run cts -m CtsInitTestCases -t init#GentleKill
      atest init#GentleKill
      Will skip under cts, pass under atest
Change-Id: I69e8be7000718bdba1c2acd9675b5645c0891afc
diff --git a/init/init_test.cpp b/init/init_test.cpp
index 1e69ede..7bb5c90 100644
--- a/init/init_test.cpp
+++ b/init/init_test.cpp
@@ -679,6 +679,10 @@
 }
 
 TEST(init, GentleKill) {
+    if (getuid() != 0) {
+        GTEST_SKIP() << "Must be run as root.";
+        return;
+    }
     std::string init_script = R"init(
 service test_gentle_kill /system/bin/sleep 1000
     disabled