rstrnt-sync-* apparently not compatible with tmt

[happz]

When called for the first time, rstrnt-sync-set spawns a background process that listens on TCP & Unix sockets for incoming sync changes. However, when a test finishes, tmt & SSH cooperate to avoid leaving leftover processes on the guest, and this means the said background process would be killed. Probably quite strongly, as it does not clean up the Unix socket, and any subsequent call to rstrnt-sync-set on the same guest, e.g. from a later test, will get stuck on trying to connect to the now dead background sync manager process.

rstrnt-sync could do a better job when starting the background process, it's still part of the test's process group, and as such it's "garbage collected" when the test finishes.

What to do with this situation? Do we want to provide compatible aliases? Or write a note & recommend other libraries?

Related issue https://issues.redhat.com/browse/TFT-2395