Make get_snmp_data more robust

[tantecky]

Description:

Handle cases when non-binary data are encounter in a SNMP response.

E.g. the following command: snmpwalk -v1 -c public myrouter 1.3.6.1.2.1.9999 returns a list of currently assigned MAC addresses from Mikrotik router:

SNMPv2-SMI::mib-2.9999.1.1.6.4.1.7.192.168.3.4 = INTEGER: 3
SNMPv2-SMI::mib-2.9999.1.1.6.4.1.7.192.168.3.2 = INTEGER: 3
SNMPv2-SMI::mib-2.9999.1.1.6.4.1.8.192.168.3.4 = Hex-STRING: 01 06 BC 5F F4 FF 03 27 
SNMPv2-SMI::mib-2.9999.1.1.6.4.1.8.192.168.3.2 = Hex-STRING: 01 06 BC 5F F4 FF 02 9C

which throws an AttributeError, because Integer does not have asOctets() method.

[mention-bot]

@tantecky, thanks for your PR! By analyzing the history of the files in this pull request, we identified @tomduijf, @fabaff and @T3m3z to be potential reviewers.

[homeassistant]

Hi @tantecky,

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Once you do that we will be able to review and accept this pull request.

Thanks!