stack/slapos: Use shacache via CDN with [download|dir].shacache.org

  This intent to speed up the download (only) of cache by using traffic server

software/test-slave-instance-deployment/software.cfg

@@ -138,5 +138,5 @@ setuptools = 0.9.8
 prettytable = 0.7.3-nxd001
 
 [networkcache]
-download-cache-url = http://www.shacache.org/shacache
-download-dir-url = http://www.shacache.org/shadir
\ No newline at end of file
+download-cache-url = http://download.shacache.org
+download-dir-url = http://dir.shacache.org

stack/shacache-client.cfg

@@ -3,5 +3,5 @@
 networkcache-section = networkcache
 
 [networkcache]
-download-cache-url = http://www.shacache.org/shacache
-download-dir-url = http://www.shacache.org/shadir
+download-cache-url = http://download.shacache.org
+download-dir-url = http://dir.shacache.org

stack/slapos.cfg

@@ -192,8 +192,8 @@ uritemplate = 3.0.0
 zope.interface = 4.3.3
 
 [networkcache]
-download-cache-url = http://www.shacache.org/shacache
-download-dir-url = http://www.shacache.org/shadir
+download-cache-url = http://download.shacache.org/
+download-dir-url = http://dir.shacache.org/
 
 # signature certificates of the following uploaders.
 #   Romain Courteaud