test: replace echo with socat
    
    The original version of the test used netcat along with a standard
    AF_UNIX socket, which caused issues across different netcat
    implementations. The AF_UNIX socket was then replaced by a FIFO with a
    simple echo, which, however, suffers from the same issue (some echo
    implementations don't check if the write() was successful).
    
    Let's revert back to the AF_UNIX socket, but replace netcat with socat,
    which, hopefully, resolves the main issue.
    
    Relevant commit: 9b45c2bf02a43e3e1b42de1ab0c3fe29c64dc5f5
    
    (cherry picked from commit b35d6d828b3216d022e565820d9971cb0f7746c1)
    
    patch_name: 0087-test-replace-echo-with-socat.patch
    present_in_specfile: true
    location_in_specfile: 87
    squash_commits: true