app_main: failure to PR_SET_NO_NEW_PRIVS is always fatal.

Don't make allowances for older kernels. Kernels must handle this
properly since it is now a CTS requirement.

Also remove some unreachable return statements.

Change-Id: I280c4ed5e461d37672236747b5dbb7d1e97ecfec
diff --git a/cmds/app_process/app_main.cpp b/cmds/app_process/app_main.cpp
index 80af5ea..18ad43e 100644
--- a/cmds/app_process/app_main.cpp
+++ b/cmds/app_process/app_main.cpp
@@ -185,12 +185,7 @@
 int main(int argc, char* const argv[])
 {
     if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) < 0) {
-        // Older kernels don't understand PR_SET_NO_NEW_PRIVS and return
-        // EINVAL. Don't die on such kernels.
-        if (errno != EINVAL) {
-            LOG_ALWAYS_FATAL("PR_SET_NO_NEW_PRIVS failed: %s", strerror(errno));
-            return 12;
-        }
+        LOG_ALWAYS_FATAL("PR_SET_NO_NEW_PRIVS failed: %s", strerror(errno));
     }
 
     AppRuntime runtime(argv[0], computeArgBlockSize(argc, argv));
@@ -309,6 +304,5 @@
         fprintf(stderr, "Error: no class name or --zygote supplied.\n");
         app_usage();
         LOG_ALWAYS_FATAL("app_process: no class name or --zygote supplied.");
-        return 10;
     }
 }