Description of problem:

scenario:
########
- host installation 

case:
#####
- host is already configured with bridge - any bridge, with regardless of its 
  name
- setNetworking function is skipped since host nic is already a part of bridge, 
  which means, host won't be able to participate in engine cluster, as it will 
  miss the required bridge name.

cause:
######

I think that the problem is with the following function, as it doesn't check if bridge exits and brdigeName == MGT_BRIDGE_NAME but only if nic is a part of bridge.

def _getBridgeParams(bridgeName):
    import shlex

    fIsBridgeDevice = False
    lstReturn = []
    fileName = IFACE_CONFIG + bridgeName

    try:
        for line in file(fileName):
            line = line.strip()
            if line.startswith("DEVICE=") or \
               line.startswith("#") or \
               line.startswith("HWADDR="):
                pass
            elif line.startswith("TYPE="):
                t = line.split("=", 1)[1].strip()
                fIsBridgeDevice = (t == "Bridge")
            else:
                try:
                    line = ''.join(shlex.split(line))
                except:
                    logging.warn("_getBridgeParams: failed to read parse line %s", line)
                lstReturn.append(line)
    except Exception, e:
        logging.error("_getBridgeParams: failed to read params of file " + fileName + ".\n Error:" + str(e))
        lstReturn = []

    return lstReturn, fIsBridgeDevice

git d68a46fe522d6e14e66cc5e093ceb9cdfb750792