[2252] remove STATS_SEND_STATISTICS_REQUEST

It is not constant whether STATS_SEND_STATISTICS_REQUEST or
XFRIN_RECEIVED_COMMAND (XFROUT_RECEIVED_GETSTATS_COMMAND) comes
first. It is not reliable to check the former one prior to the latter
one.  Eventually the latter one is an important event so the former
one is removed.

tests/lettuce/features/xfrin_notify_handling.feature

@@ -54,7 +54,6 @@ Feature: Xfrin incoming notify handling
 
     # wait until the last stats requesting is finished
     When I query statistics zones of bind10 module Xfrout with cmdctl port 47804
-    wait for new master stderr message STATS_SEND_STATISTICS_REQUEST
     wait for new master stderr message XFROUT_RECEIVED_GETSTATS_COMMAND
     last bindctl output should not contain "error"
 
@@ -80,7 +79,6 @@ Feature: Xfrin incoming notify handling
 
     # wait until the last stats requesting is finished
     When I query statistics zones of bind10 module Xfrin with cmdctl
-    wait for new bind10 stderr message STATS_SEND_STATISTICS_REQUEST
     wait for new bind10 stderr message XFRIN_RECEIVED_COMMAND
     last bindctl output should not contain "error"
 
@@ -179,7 +177,6 @@ Feature: Xfrin incoming notify handling
 
     # wait until the last stats requesting is finished
     When I query statistics zones of bind10 module Xfrin with cmdctl
-    wait for new bind10 stderr message STATS_SEND_STATISTICS_REQUEST
     wait for new bind10 stderr message XFRIN_RECEIVED_COMMAND
     last bindctl output should not contain "error"
 
@@ -257,7 +254,6 @@ Feature: Xfrin incoming notify handling
 
     # wait until the last stats requesting is finished
     When I query statistics zones of bind10 module Xfrout with cmdctl port 47804
-    wait for new master stderr message STATS_SEND_STATISTICS_REQUEST
     wait for new master stderr message XFROUT_RECEIVED_GETSTATS_COMMAND
     last bindctl output should not contain "error"
 
@@ -286,7 +282,6 @@ Feature: Xfrin incoming notify handling
 
     # wait until the last stats requesting is finished
     When I query statistics zones of bind10 module Xfrin with cmdctl
-    wait for new bind10 stderr message STATS_SEND_STATISTICS_REQUEST
     wait for new bind10 stderr message XFRIN_RECEIVED_COMMAND
     last bindctl output should not contain "error"
 
@@ -393,7 +388,6 @@ Feature: Xfrin incoming notify handling
 
     # wait until the last stats requesting is finished
     When I query statistics zones of bind10 module Xfrin with cmdctl
-    wait for new bind10 stderr message STATS_SEND_STATISTICS_REQUEST
     wait for new bind10 stderr message XFRIN_RECEIVED_COMMAND
     last bindctl output should not contain "error"