Upgrade rcjava2 2.1.8

Author: slandelle

pom.xml

@@ -387,7 +387,7 @@
 		<reactive-streams.version>1.0.2</reactive-streams.version>
 		<netty-reactive-streams.version>2.0.0</netty-reactive-streams.version>
 		<rxjava.version>1.3.4</rxjava.version>
-		<rxjava2.version>2.1.7</rxjava2.version>
+		<rxjava2.version>2.1.8</rxjava2.version>
 		<logback.version>1.2.3</logback.version>
 		<testng.version>6.13.1</testng.version>
 		<jetty.version>9.4.8.v20171121</jetty.version>