Refactor solution. Remove systemd changes and associated bash script.

Make call to clear rmtab from nfs.setup_directories.
Cannot use middleware setup hook because /var/db/system/nfs is not yet available at that point.

src/freenas/etc/systemd/system/nfs-server.service.d/override.conf

@@ -1,6 +1,3 @@
 [Unit]
 ConditionDirectoryNotEmpty=!/etc/exports.d
 After=nslcd.service
-
-[Service]
-ExecStartPre=/usr/local/bin/clear_nfs_rmtab.sh

src/middlewared/middlewared/plugins/nfs.py

@@ -188,6 +188,12 @@ def setup_directories(self):
             except Exception:
                 self.logger.error('Unexpected failure initializing %r', path, exc_info=True)
 
+        # Clear rmtab on boot.
+        # We call this here because /var/db/system/nfs is not yet available
+        # in a middleware 'setup' hook.
+        if not self.middleware.call_sync('system.ready'):
+            self.middleware.call_sync('nfs.clear_nfs3_rmtab')
+
     @private
     async def nfs_extend(self, nfs):
         keytab_has_nfs = await self.middleware.call("kerberos.keytab.has_nfs_principal")