[FIX] do only store password if LDAP_Login_Fallback is on

[pmb0]

@RocketChat/core
@TwizzyDizzy

See #6144

Comment by TwizzyDizzy

We do NOT want passwords to be saved in MongoDB when LDAP is enabled (this might be made into an option in the backend, if not, they should not be saved by default)
unless fallback-login is activated
this means the passwords need to be erased (for LDAP-flagged accounts) on disabling fallback login and stored on next login, when this feature is enabled

This PR changes the password storage behaviour if LDAP_Login_Fallback is enabled. The password will not be saved in MongoDB.

[CLAassistant]

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[magicbelette]

Rocket.Chat Version: 0.57.1

Passwords are still stored when create new user :

// Create new user
return addLdapUser(ldapUser, username, loginRequest.ldapPass);

Need to check "LDAP_Login_Fallback" setting again :

if (RocketChat.settings.get('LDAP_Login_Fallback') === true) {
   return addLdapUser(ldapUser, username, loginRequest.ldapPass);        
} else {
   return addLdapUser(ldapUser, username);
}