netperf: use alarm timer for setting timeouts

Fixes #1021
os: manage/dissolve Signal_rpc_member in class

Instead of, passing responsibility to manage and dissolve Signal_rpc_member
objects at a corresponding entrypoint to the user, hand over entrypoint's
reference to the constructor, and do it in the constructor resp. destructor
of the class.

Fixes #1022
block: fix race in generic block driver component

Fixes #1023