Only remove the maven-javadoc-plugin configuration on EPEL 8

Add source version to javadoc configuration (backported from git)

voms-api-java-javadoc-source.patch

@@ -0,0 +1,24 @@
+From f0fd4e08e94d70630d7948da2a8e2acf2a337697 Mon Sep 17 00:00:00 2001
+From: Mattias Ellert <mattias.ellert@physics.uu.se>
+Date: Tue, 19 Feb 2019 18:50:10 +0100
+Subject: [PATCH] Add source version to javadoc configuration
+
+---
+ pom.xml | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/pom.xml b/pom.xml
+index 82005e5..8ce8467 100644
+--- a/pom.xml
++++ b/pom.xml
+@@ -138,6 +138,7 @@
+         <artifactId>maven-javadoc-plugin</artifactId>
+         <version>${plugin.javadoc.version}</version>
+         <configuration>
++          <source>1.8</source>
+           <outputDirectory>${project.build.directory}/javadoc</outputDirectory>
+           <reportOutputDirectory>${project.reporting.outputDirectory}/javadoc</reportOutputDirectory>
+         </configuration>
+-- 
+2.25.4
+