docker: put cqlsh configuration in correct place

since always we were putting cqlsh configuration into `~/.cqlshrc`
acording to commit from 8 years ago [1], this path is deprecated.

until this commit [2], actully remove this path from cqlsh code

as part of moving to scylla-cqlsh, we got [2], and didn't
notice until the first release with it.

this change write the configuration into `~/.casssndra/cqlshrc`
as this is the default place cqlsh is looking.

[1]: 13ea8a6669/bin/cqlsh.py (L264)
[2]: 2024ea4796
Fixes: scylladb/scylladb#16329

Closes scylladb/scylladb#16340

dist/docker/scyllasetup.py

@@ -75,7 +75,8 @@ class ScyllaSetup:
             hostname = self._listenAddress
         else:
             hostname = subprocess.check_output(['hostname', '-i']).decode('ascii').strip()
-        with open("%s/.cqlshrc" % home, "w") as cqlshrc:
+        self._run(["mkdir", "-p",  "%s/.cassandra" % home])
+        with open("%s/.cassandra/cqlshrc" % home, "w") as cqlshrc:
             cqlshrc.write("[connection]\nhostname = %s\n" % hostname)
 
     def set_housekeeping(self):