[MM-63314] Fix ClaimJob in HA environments (#30383)

* ClaimJob now returns newly claimed job

* internal code affected by change

* test changes required

* two branches: for mysql, use transaction; for postgres, use returning

* two branches: for mysql, use transaction; for postgres, use returning

* use same millis value for LastActivityAt and StartAt

* blank commit

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/store/sqlstore/utils.go

@@ -5,6 +5,7 @@ package sqlstore
 
 import (
 	"database/sql"
+	"errors"
 	"fmt"
 	"io"
 	"net/url"
@@ -54,7 +55,7 @@ func MapStringsToQueryParams(list []string, paramPrefix string) (string, map[str
 // finalizeTransactionX ensures a transaction is closed after use, rolling back if not already committed.
 func finalizeTransactionX(transaction *sqlxTxWrapper, perr *error) {
 	// Rollback returns sql.ErrTxDone if the transaction was already closed.
-	if err := transaction.Rollback(); err != nil && err != sql.ErrTxDone {
+	if err := transaction.Rollback(); err != nil && !errors.Is(err, sql.ErrTxDone) {
 		*perr = merror.Append(*perr, err)
 	}
 }