kernel: Utilise the existing try_umount to avoid repackaging

kernel/kernel_umount.h

@@ -6,6 +6,8 @@
 void ksu_kernel_umount_init(void);
 void ksu_kernel_umount_exit(void);
 
+void try_umount(const char *mnt, bool check_mnt, int flags);
+
 // Handler function to be called from setresuid hook
 int ksu_handle_umount(uid_t old_uid, uid_t new_uid);