Define HAS_LXC even if import lxc doesn't fail.

This fixes::

    Traceback (most recent call last):
      File "/home/jpic/.ansible/tmp/ansible-tmp-1435080800.61-38257321141340/lxc_container", line 3353, in <module>
        main()
      File "/home/jpic/.ansible/tmp/ansible-tmp-1435080800.61-38257321141340/lxc_container", line 1712, in main
        if not HAS_LXC:
    NameError: global name 'HAS_LXC' is not defined

lib/ansible/modules/extras/cloud/lxc/lxc_container.py

@@ -385,6 +385,8 @@ try:
     import lxc
 except ImportError:
     HAS_LXC = False
+else:
+    HAS_LXC = True
 
 
 # LXC_COMPRESSION_MAP is a map of available compression types when creating