server: do not set opentracing span context  unnecessarily (#23326)
server: do not set opentracing span context  unnecessarily (#23326)

 
ngaut/tidb,ngaut/tidb,pingcap/tidb,c4pt0r/tidb,kyle-wang/tidb,kyle-wang/tidb,kyle-wang/tidb,pingcap/tidb,kyle-wang/tidb,kyle-wang/tidb,pingcap/tidb,ngaut/tidb,c4pt0r/tidb,ngaut/tidb,pingcap/tidb,ngaut/tidb,c4pt0r/tidb,coocood/tidb,ngaut/tidb,kyle-wang/tidb,c4pt0r/tidb,pingcap/tidb,c4pt0r/tidb,pingcap/tidb,c4pt0r/tidb,coocood/tidb