staticcheck found a couple of minor code cleanup improvements, like
unused variables or an out-of-order defer, mostly in tests.
This patch fixes those problems by making the necessary adjustments.
They're all fairly small, and should not change the logic in any
significant way.
The testing package does not allow t.Fatal to be called from a different
goroutine; however, we do that if the testing server fails listen or
accept connections.
Since that is unexpected and rare, this patch turns those calls into
panics.
This patch adds a new package for doing local lightweight RPC calls over UNIX
sockets. This will be used in later patches for communication between chasquid
and chasquid-util.
