When an invalid socket path is passed to -ipcconnect, either because the path
exceeds the maximum socket length, or the path includes a directory component
which is not actually a directory, treat this the same as the same as the
socket refusing connections or not existing, instead of treating it like a more
serious I/O error and throwing a fatal exception.
This is needed to avoid CI errors after the following commit which adds a
functional test and uses -datadir paths exceeding the maximum socket length
when running in CI.
0448a19b1b