fix handling of nics argument

The existing code was receiving a list of strings and erroneously
assuming it was being given a list of dictionaries, leading it to fail
with:

    AttributeError: 'str' object has no attribute 'get'

This commit corrects the list handling code to check the type of each
item and handle it appropriately.   Also, based on bcoca's comment
in #2253, thie code removes the special case for a string-only argument.

By transforming string arguments into dicts and then handling them like
any other dict argument, this also permits arguments of the form:

    nics: net-name=mynet

Or:

    nics: port-name=mynet

Previous versions of this code only supported `net-id` and `port-id` in
string specifications.

lib/ansible/modules/cloud/openstack/os_server.py

@@ -86,8 +86,8 @@ options:
         - A list of networks to which the instance's interface should
           be attached. Networks may be referenced by net-id/net-name/port-id
           or port-name.
-        - 'Also this accepts a string containing a list of net-id/port-id.
-          Eg: nics: "net-id=uuid-1,net-id=uuid-2"'
+        - 'Also this accepts a string containing a list of (net/port)-(id/name)
+          Eg: nics: "net-id=uuid-1,port-name=myport"'
      required: false
      default: None
    auto_ip:
@@ -288,17 +288,19 @@ def _exit_hostvars(module, cloud, server, changed=True):
         changed=changed, server=server, id=server.id, openstack=hostvars)
 
 
+def _parse_nics(nics):
+    for net in nics:
+        if type(net) == str:
+            for nic in net.split(','):
+                yield dict((nic.split('='),))
+        else:
+            yield net
+
 def _network_args(module, cloud):
     args = []
     nics = module.params['nics']
-    if type(nics) == str :
-        for kv_str in nics.split(","):
-            nic = {}
-            k, v = kv_str.split("=")
-            nic[k] = v
-            args.append(nic)
-    else:
-        for net in module.params['nics']:
+
+    for net in _parse_nics(nics):
         if net.get('net-id'):
             args.append(net)
         elif net.get('net-name'):