rework SNMP probing logic

SNMPv3 seems to raise exceptions at session creation for non-responding
host, or for invalid response, whereas other protocol version suceed but
fails to get any result thereafter.
add compile() and isPartOf() functions
handle push request more selectively

When receiving a push request from a given server, and multiple servers
are configured, there is no need to contact all of them.
rename resolv() to resolve()
kill spurious whitespace
useless variable
fix test
useless variable
just test ifconfig parsing result

The result of _getInterfaces relies on additional external commands,
such as /usr/sbin/ndd, to compute interface speed, which makes it
unsuitable for testing on Solaris platform.

closes: #2438