Make test suite logs prettier

This fixes a few issues with the unit test logs that make them ugly:
1. Currently some lines of output from a command will appear after the
   line from xtrace which has the next command, since the command was
   printing to stdout and xtrace uses stderr. E.g. "Installation complete."
   will appear after "+ flatpak --user install -y ..." but it is from the
   previous install command.
2. Lines of output have many spaces after them to pad them to the table
   width but this is not needed for non-fancy output.
3. Lines of output are mixed with output from httpd since they don't end
   with a newline character, e.g. "Installing… ▊
   4%127.0.0.1 - - [16/Nov/2021 00:18:24] "GET /..."

(cherry picked from commit 388c23cfc51b6b9f03dcdf87b11c0078f11227ea)