Assignment operator does not check for self-assignment

Defect 73597 (STATIC_C)
Checker SELF_ASSIGN (subcategory none)
File: /src/mongo/s/catalog/forwarding_catalog_manager.cpp
Function mongo::ForwardingCatalogManager::ScopedDistLock::operator =(mongo::ForwardingCatalogManager::ScopedDistLock&&)
/src/mongo/s/catalog/forwarding_catalog_manager.cpp, line: 423
No protection against the object assigning to itself.

        _fcm = other._fcm;