Fixing casual failing of nc service in LBaaS

Netcat quits after first web connection to it, causing test
to fail with HTTP 503 error. In Cirros 0.3.3 nc doesn't support
"-ll" option for persistence listening.
Added catching HTTP exceptions, and infinite cycle for netcat.
Fixed network finding. Fixed command string to be more pythonic.
Closes-Bug: #1384708

Change-Id: Ib9c9cd3d0040003d0296426d8a7ce800c193f22b
diff --git a/tempest/scenario/test_load_balancer_basic.py b/tempest/scenario/test_load_balancer_basic.py
index d061406..7240208 100644
--- a/tempest/scenario/test_load_balancer_basic.py
+++ b/tempest/scenario/test_load_balancer_basic.py
@@ -125,8 +125,8 @@
         keypair = self.create_keypair()
         security_groups = [self.security_group]
         create_kwargs = {
-            'nics': [
-                {'net-id': self.network['id']},
+            'networks': [
+                {'uuid': self.network['id']},
             ],
             'key_name': keypair['name'],
             'security_groups': security_groups,
@@ -170,9 +170,9 @@
                 private_key=private_key)
 
             # Write a backend's response into a file
-            resp = """echo -ne "HTTP/1.1 200 OK\r\nContent-Length: 7\r\n""" \
-                   """Connection: close\r\nContent-Type: text/html; """ \
-                   """charset=UTF-8\r\n\r\n%s"; cat >/dev/null"""
+            resp = ('echo -ne "HTTP/1.1 200 OK\r\nContent-Length: 7\r\n'
+                    'Connection: close\r\nContent-Type: text/html; '
+                    'charset=UTF-8\r\n\r\n%s"; cat >/dev/null')
 
             with tempfile.NamedTemporaryFile() as script:
                 script.write(resp % server_name)
@@ -186,8 +186,9 @@
                                                username, key.name)
 
             # Start netcat
-            start_server = """sudo nc -ll -p %(port)s -e sh """ \
-                           """/tmp/%(script)s &"""
+            start_server = ('while true; do '
+                            'sudo nc -l -p %(port)s -e sh /tmp/%(script)s; '
+                            'done &')
             cmd = start_server % {'port': self.port1,
                                   'script': 'script1'}
             ssh_client.exec_command(cmd)
@@ -215,6 +216,8 @@
                 return False
             except IOError:
                 return False
+            except urllib2.HTTPError:
+                return False
         timeout = config.compute.ping_timeout
         start = time.time()
         while not try_connect(check_ip, port):
@@ -297,8 +300,13 @@
     def _send_requests(self, vip_ip, servers):
         counters = dict.fromkeys(servers, 0)
         for i in range(self.num):
-            server = urllib2.urlopen("http://{0}/".format(vip_ip)).read()
-            counters[server] += 1
+            try:
+                server = urllib2.urlopen("http://{0}/".format(vip_ip)).read()
+                counters[server] += 1
+            # HTTP exception means fail of server, so don't increase counter
+            # of success and continue connection tries
+            except urllib2.HTTPError:
+                continue
         # Assert that each member of the pool gets balanced at least once
         for member, counter in counters.iteritems():
             self.assertGreater(counter, 0, 'Member %s never balanced' % member)