concoredocker.hpp paths dont match python + retry is broken #349

Two issues in the docker C++ implementation....

First - path construction is wrong. Python does os.path.join(inpath, str(port), name) which gives /in/1/data but C++ concatenates as inpath + std::to_string(port) + "/" + name which gives /in1/data - missing the slash after inpath. So python nodes and C++ nodes write to completely different directories and can't communicate at all

Second - the retry loop doesn't work. Line ~152 opens the file with std::ifstream infile(file_path), then in the retry loop it calls infile.open(file_path) again. But if you call open() on an already-opened ifstream it just sets failbit and all subsequent reads fail silently. So the retry never actually retries, it just loops 5 times returning empty string then gives up

You can repro #1 by putting a python writer and C++ reader in the same docker graph - reader won't find the files. For #2 just have any file that takes a moment to appear and watch the retry do nothing

Fix would be-

add "/" after inpath in path construction,
either close() the stream before reopening or just make a new ifstream each loop iteration

btw this is on docker desktop/windows but the path issue will break anywhere and the retry thing is just how C++ streams work