Seastar uses POSIX IO for output in addition to C++ iostreams, e.g. in print_safe(), where it write()s directly to stdout. Instead of manipulating C++ output streams to reset stdout/log files, reopen the underlying file descriptors to output/log files. Fixes #9962 "cql_repl prints junk into the log" Message-Id: <20220204205032.1313150-1-kostja@scylladb.com>