Synchronized block in AbstractAuthorizationGrantHandler causes DB connection issue

[ruwanta]

Description:
There is a syncronized block in AbstractAuthorizationGrantHandler

 public OAuth2AccessTokenRespDTO issue(OAuthTokenReqMessageContext tokReqMsgCtx) throws IdentityOAuth2Exception 

synchronized ((consumerKey + ":" + authorizedUser + ":" + scope).intern())
...
dbCalls()
...

This causes long running DB queries to timeout all other similar calls, with ThreadDeath
We need to improve this syncronization to handle at the DB level, as the syncronization does not help on cluster/multi-node scenario.