Rename list_updates to list_upgrades

In preparation for #3210, rename list_updates to list_upgrades. Also,
link list_updates to list_upgrade so that people used to running "zypper
list-updates" from the command line will still see the available
upgrades.

Hide list_updates from sphinx docs.

doc/ref/modules/all/salt.modules.zypper.rst

@@ -3,4 +3,5 @@ salt.modules.zypper
 ===================
 
 .. automodule:: salt.modules.zypper
-    :members:
+    :members:
+    :exclude-members: list_updates

salt/modules/zypper.py

@@ -34,9 +34,13 @@ def _list_removed(old, new):
     return pkgs
 
 
-def list_updates():
+def list_upgrades():
     '''
-    List packages with updates. Returns a dict of pkg/version pairs.
+    List all available package upgrades on this system
+
+    CLI Example::
+
+        salt '*' pkg.list_upgrades
     '''
     ret = {}
     out = __salt__['cmd.run_stdout']('zypper list-updates').splitlines()
@@ -47,13 +51,16 @@ def list_updates():
             continue
         try:
             status, repo, name, cur, avail, arch = \
-            [x.strip() for x in line.split('|')]
+                [x.strip() for x in line.split('|')]
         except ValueError, IndexError:
             continue
         if status == 'v':
             ret[name] = avail
     return ret
 
+# Provide a list_updates function for those used to using zypper list-updates
+list_updates = list_upgrades
+
 
 def available_version(*names):
     '''
@@ -72,7 +79,7 @@ def available_version(*names):
     if len(names) == 0:
         return ''
     ret = {}
-    updates = list_updates()
+    updates = list_upgrades()
     for name in names:
         ret[name] = updates.get(name, '')