fs_mgr: Support nosymfollow mount option

Summary: The nosymfollow mount option was added to Linux 5.10, and the bionic
headers support it. Allow mounting with the option set. Updated relevant
CTS test too.

Test: Successful build on master

Change-Id: I0b280287e07ef8c485762b820dbbb26300144982
Signed-off-by: Abdelrahman Daim <adaim@meta.com>
diff --git a/init/builtins.cpp b/init/builtins.cpp
index c4af5b5..38aed9c 100644
--- a/init/builtins.cpp
+++ b/init/builtins.cpp
@@ -471,6 +471,7 @@
     { "private",    MS_PRIVATE },
     { "slave",      MS_SLAVE },
     { "shared",     MS_SHARED },
+    { "nosymfollow", MS_NOSYMFOLLOW },
     { "defaults",   0 },
     { 0,            0 },
 };