Fix collision in random filter name by merging functionality

Merges the functionality of the original jinja2 random filter with
the one we provide.

Fixes #7113

docsite/rst/playbooks_variables.rst

@@ -241,6 +241,13 @@ Random Number Filter
 
 .. versionadded:: 1.6
 
+This filter can be used similar to the default jinja2 random filter (returning a random item from a sequence of
+items), but can also generate a random number based on a range.
+
+To get a random item from a list::
+
+    {{ ['a','b','c']|random }} => 'c'
+
 To get a random number from 0 to supplied end::
 
     {{ 59 |random}} * * * * root /script/from/cron

lib/ansible/runner/filter_plugins/core.py

@@ -181,9 +181,20 @@ def version_compare(value, version, operator='eq', strict=False):
     except Exception, e:
         raise errors.AnsibleFilterError('Version comparison: %s' % e)
 
-def rand(end, start=0, step=1):
+def rand(end, start=None, step=None):
     r = SystemRandom()
+    if isinstance(end, (int, long)):
+        if not start:
+            start = 0
+        if not step:
+            step = 1
         return r.randrange(start, end, step)
+    elif hasattr(end, '__iter__'):
+        if start or step:
+            raise errors.AnsibleFilterError('start and step can only be used with integer values')
+        return r.choice(end)
+    else:
+        raise errors.AnsibleFilterError('random can only be used on sequences and integers')
 
 class FilterModule(object):
     ''' Ansible core jinja2 filters '''