Support nonce based web login

Support the newer web loogin procedure that requires a nonce to
get going.

Change-Id: Ia6c532f0e18d2b101ca9cd9ba1c539fdedea2862

pyghmi/ipmi/oem/lenovo/imm.py

@@ -1035,10 +1035,19 @@ class XCCClient(IMMClient):
         adata = json.dumps({'username': self.username,
                             'password': self.password
                             })
+        nonce = None
+        wc.request('POST', '/api/providers/get_nonce', '{}')
+        rsp = wc.getresponse()
+        tokbody = rsp.read()
+        if rsp.status == 200:
+            rsp = json.loads(tokbody)
+            nonce = rsp.get('nonce', None)
         headers = {'Connection': 'keep-alive',
                    'Referer': 'https://xcc/',
                    'Host': 'xcc',
                    'Content-Type': 'application/json'}
+        if nonce:
+            headers['Content-Security-Policy'] = 'nonce={0}'.format(nonce)
         wc.request('POST', '/api/login', adata, headers)
         rsp = wc.getresponse()
         if rsp.status == 200: