[SPARK-8649] [BUILD] Mapr repository is not defined properly

The previous commiter on this part was pwendell

The previous url gives 404, the new one seems to be OK.

This patch is added under the Apache License 2.0.

The JIRA link: https://issues.apache.org/jira/browse/SPARK-8649

Author: Thomas Szymanski <develop@tszymanski.com>

Closes #7054 from tszym/SPARK-8649 and squashes the following commits:

bfda9c4 [Thomas Szymanski] [SPARK-8649] [BUILD] Mapr repository is not defined properly

pom.xml

@@ -248,7 +248,7 @@
     <repository>
       <id>mapr-repo</id>
       <name>MapR Repository</name>
-      <url>http://repository.mapr.com/maven</url>
+      <url>http://repository.mapr.com/maven/</url>
       <releases>
         <enabled>true</enabled>
       </releases>