Allow boolean values to pass through to glance

When uploading an image it is necessary to set flags such as
protected=True. Currently the code blindly converts everything to a
string leading to errors. This change will allow booleans to pass
through unmolested.

Change-Id: Ib0e230cf9c52500973ac2e7636f3dc607c1e8089

shade/openstackcloud.py

@@ -2931,6 +2931,8 @@ class OpenStackCloud(object):
             else:
                 if v is None:
                     ret[k] = None
+                elif isinstance(v, bool):
+                    ret[k] = v
                 else:
                     ret[k] = str(v)
         ret.update(meta)