Mssql driver update (#2610)

* Switching driver from mssql to sqlserver
* Adding explicit database to sp_msloginmappings call

builtin/logical/mssql/backend.go

@@ -78,7 +78,7 @@ func (b *backend) DB(s logical.Storage) (*sql.DB, error) {
 	}
 	connString := connConfig.ConnectionString
 
-	db, err := sql.Open("mssql", connString)
+	db, err := sql.Open("sqlserver", connString)
 	if err != nil {
 		return nil, err
 	}

builtin/logical/mssql/secret_creds.go

@@ -102,7 +102,7 @@ func (b *backend) secretCredsRevoke(
 	// we need to drop the database users before we can drop the login and the role
 	// This isn't done in a transaction because even if we fail along the way,
 	// we want to remove as much access as possible
-	stmt, err := db.Prepare(fmt.Sprintf("EXEC sp_msloginmappings '%s';", username))
+	stmt, err := db.Prepare(fmt.Sprintf("EXEC master.dbo.sp_msloginmappings '%s';", username))
 	if err != nil {
 		return nil, err
 	}