Remove useless information on "show run-config" with "bridge + 8021q" implementation

[claudiughioc]

!
hostname centos6.localdomain
!
!
no ip igmp snooping
!
interface Ethernet 3
switchport trunk allowed vlan 1-4094
switchport mode access
!
mac-address-table static 0800.2761.80ed vlan 1 interface Ethernet 3
mac-address-table aging-time 0
!

Possible bugs:
* "switchport trunk allowed vlan" shouldn't be there unless other
vlans than all (which is the case here) are configured
* "switchport mode access" shouldn't be there since it's the
default
* static mac 0800.2761.80ed shouldn't be there since no one
configured it; it's equal to the bridge id, which in turn is
equal to the mac of the first added interface; "brctl showmacs"
lists it as local=yes - perhaps "local" macs should be filtered
out?