microdroid runs in a single mount namespace

Since there's no two separate mount namespace, we don't need to
"enter_default_mount_ns".

Bug: 185991357
Test: MicrodroidHostTestCases
Change-Id: I0bea5ef51da95c378ade1288c36d4cab91266ab2
diff --git a/microdroid/init.rc b/microdroid/init.rc
index 614a5ed..45d9398 100644
--- a/microdroid/init.rc
+++ b/microdroid/init.rc
@@ -15,11 +15,6 @@
     # set RLIMIT_NICE to allow priorities from 19 to -20
     setrlimit nice 40 40
 
-    # in microdroid, we don't use "bootstrap" mount namespace
-    # because APEXes are passed from host and are available
-    # from the start. We don't need to wait till /data is ready.
-    enter_default_mount_ns
-
     start ueventd
 
     # TODO(b/190343842) verify apexes/apk before mounting them.