SPARK-1254. Supplemental fix for HTTPS on Maven Central

It seems that HTTPS does not necessarily work on Maven Central, as it does not today at least. Back to HTTP. Both builds works from a clean repo.

Author: Sean Owen <sowen@cloudera.com>

Closes #209 from srowen/SPARK-1254Fix and squashes the following commits:

bb7be47 [Sean Owen] Revert to HTTP for Maven Central repo, as it seems HTTPS does not necessarily work

pom.xml

@@ -132,7 +132,8 @@
     <repository>
       <id>maven-repo</id> <!-- This should be at top, it makes maven try the central repo first and then others and hence faster dep resolution -->
       <name>Maven Repository</name>
-      <url>https://repo.maven.apache.org/maven2</url>
+      <!-- HTTPS is unavailable for Maven Central -->
+      <url>http://repo.maven.apache.org/maven2</url>
       <releases>
         <enabled>true</enabled>
       </releases>

project/SparkBuild.scala

@@ -182,7 +182,8 @@ object SparkBuild extends Build {
     concurrentRestrictions in Global += Tags.limit(Tags.Test, 1),
 
     resolvers ++= Seq(
-      "Maven Repository"     at "https://repo.maven.apache.org/maven2",
+      // HTTPS is unavailable for Maven Central
+      "Maven Repository"     at "http://repo.maven.apache.org/maven2",
       "Apache Repository"    at "https://repository.apache.org/content/repositories/releases",
       "JBoss Repository"     at "https://repository.jboss.org/nexus/content/repositories/releases/",
       "MQTT Repository"      at "https://repo.eclipse.org/content/repositories/paho-releases/",