Upgrade to httpasyncclient to 4.1.1

Closes gh-4480

Author: philwebb

spring-boot-dependencies/pom.xml

@@ -82,7 +82,7 @@
 		<hikaricp-java6.version>2.3.12</hikaricp-java6.version>
 		<hornetq.version>2.4.7.Final</hornetq.version>
 		<hsqldb.version>2.3.3</hsqldb.version>
-		<httpasyncclient.version>4.1</httpasyncclient.version>
+		<httpasyncclient.version>4.1.1</httpasyncclient.version>
 		<httpclient.version>4.5.1</httpclient.version>
 		<httpcore.version>4.4.4</httpcore.version>
 		<infinispan.version>8.0.1.Final</infinispan.version>