init: start ueventd in the default mount namespace

Init starts ueventd in the default mount namespace to support loading
firmware from APEXes.

Bug: 155023652
Test: devices boots
      adb$ nsenter -t (pid of ueventd) -m ls /apex
      => shows all APEXes
Change-Id: Ibb8b33a07eb014752275e3bca4541b8b694dc64b
diff --git a/init/reboot.cpp b/init/reboot.cpp
index ffd58a3..ec92361 100644
--- a/init/reboot.cpp
+++ b/init/reboot.cpp
@@ -831,7 +831,7 @@
         sub_reason = "apex";
         return result;
     }
-    if (!SwitchToBootstrapMountNamespaceIfNeeded()) {
+    if (!SwitchToMountNamespaceIfNeeded(NS_BOOTSTRAP)) {
         sub_reason = "ns_switch";
         return Error() << "Failed to switch to bootstrap namespace";
     }