Description of problem:
getVdsCaps report  'cfg': {'BOOTPROTO': 'none'} when ifcfg-ovirtmgmt have BOOTPROTO=dhcp 

ifcfg-ovirtmgmt:
# Generated by VDSM version 4.16.0-27.git00146ed.el6
DEVICE=ovirtmgmt
ONBOOT=no
TYPE=Bridge
DELAY=0
STP=off
BOOTPROTO=dhcp
MTU=1500
DEFROUTE=yes
NM_CONTROLLED=no
HOTPLUG=no



getVdsCaps:
'ovirtmgmt': {'addr': '10.35.128.17',
                                  'bootproto4': 'none',
                                  'bridged': True,
                                  'cfg': {'BOOTPROTO': 'none',
                                          'DEFROUTE': 'yes',
                                          'DELAY': '0',
                                          'DEVICE': 'ovirtmgmt',
                                          'HOTPLUG': 'no',
                                          'MTU': '1500',
                                          'NM_CONTROLLED': 'no',
                                          'ONBOOT': 'no',
                                          'STP': 'off',
                                          'TYPE': 'Bridge'},
                                  'gateway': '10.35.128.254',
                                  'iface': 'ovirtmgmt',
                                  'ipv4addrs': ['10.35.128.17/24'],
                                  'ipv6addrs': ['fe80::216:36ff:fe84:745e/64'],
                                  'ipv6gateway': '::',
                                  'mtu': '1500',
                                  'netmask': '255.255.255.0',
                                  'ports': ['eth0'],
                                  'stp': 'off'}}


VDSM should not override bootproto if one exist in ifcfg file


Version-Release number of selected component (if applicable):
vdsm-4.16.0-27.git00146ed.el6.x86_64

How reproducible:
100%

Steps to Reproduce:
1.run vdsClient getVdsCaps