Revert "alternative method to detect remote devices"

This reverts commit 5a2122c704d34d968f73d2836dd978f31a9f32e8, too
intrusive for a bugfix branch.
Revert "use default OID if missing in model"

This reverts commit dd327fcbc95ebc58a78d56760c7b1d3e016283f3, too
intrusive for a bugfix branch.
fix incomplete commit #6a07f01

Raise timeout value for SNMP v1 and v2, as well as for reconnection with
a new community.