SLING-8888 Upgrade Karaf to 4.3.0

Use Karaf 4.3.0.RC1
diff --git a/pom.xml b/pom.xml
index fce0c89..ad0e6cd 100644
--- a/pom.xml
+++ b/pom.xml
@@ -70,7 +70,7 @@
       <groupId>org.apache.karaf</groupId>
       <artifactId>apache-karaf</artifactId>
       <type>tar.gz</type>
-      <version>4.2.6</version>
+      <version>4.3.0.RC1</version>
       <scope>test</scope>
       <exclusions>
         <exclusion>