database locking improved for login performance

A slowness issue seen when trying to login to my.pega.com was traced to numerous database locks occurring on the pr_data_saml_authreqcontext table during the SAML flow. Analysis showed that while running Obj-Save on AuthRequestContext with 'OnlyIfNew' as false, the check caused a select query to run on the table to determine if the context was already there and insert it if it was not. To resolve this, the onlyIfNew check will default to true to avoid running the query; if the context is already present it will be overridden. Duplicate key exception handling has also been added to avoid any issues if a resave is done with same key.