Revert "backported the fix for RavenDB_1379 from 3.0 to 2.5"

This reverts commit a9ee52380302490e9dffff88289ad75753fdb3cc.

Conflicts:
	Raven.Database/DocumentDatabase.cs
Revert "backported the fix for RavenDB_1379 from 3.0 to 2.5"

This reverts commit a9ee52380302490e9dffff88289ad75753fdb3cc.

Conflicts:
	Raven.Database/DocumentDatabase.cs
Moving to await/async impl for async hi lo key gen
If we match on the tx etag, we don't need to continue checking