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>