snmp v1 support

[lroussanne]

Hi,

I'm a beginner in GitHub, I don't know how to propose an improvment.

Here is mine : in _get_snmp_security

add the folowing : elif self.version == 1: return cmdgen.CommunityData(self.community, self.community,0)

before

Default to version 2c

This will add support for snmp v1 equipments

Hope you like this ;)

Laurent.