pamModuleIsThreadSafe is missing in the schema

**Issue Description**
The ticket #5271 introduces the PAM config attribute: pamModuleIsThreadSafe
It is missing in the schema 

**Package Version and Platform:**
#5271 being applied 1.3.10 and after, this ticket also impact those release

**Steps to Reproduce**
N/A

**Expected results**
pamModuleIsThreadSafe should be described in the schema (pam-plugin.ldif)
