fix(xcat-core): the error-command test writes the log archive to /run

The first subiquity error command redirects into /run/#HOSTNAME#-logs.tar. A
test can shadow tar, but not the redirection: the shell opens that file
whether or not tar runs, so the test writes to the host it runs on. Unprivileged
the open fails and "exit 0" hides it; CI runs as root, where the same line
creates or truncates the file.

The path is read from XCAT_ERROR_ARCHIVE, falling back to the same default, the
way XCAT_ERROR_CONSOLE already does on the next line. An install sets neither
variable and writes where it always did.

The test points the variable inside BATS_TEST_TMPDIR, has the tar shadow emit a
marker so the output can be traced to the file it named, and asserts the default
path under /run was not touched. Reverting the template to the fixed path fails
that case.

Signed-off-by: Daniel Hilst <392820+dhilst@users.noreply.github.com>

xCAT-server/share/xcat/install/ubuntu/compute.subiquity.tmpl

@@ -130,5 +130,8 @@ autoinstall:
     # Subiquity waits for every error command to return. "nc -l 8080" waits for a collector, which
     # an unattended install does not have. Keep the archive on the installer, and print the end of
     # the curtin log to the console, which the management node records.
-    - ['sh', '-c', 'tar -c --ignore-failed-read --transform="s/^/#HOSTNAME#-logs\//" /var/crash /var/log/installer /tmp/pre-install.log /autoinstall.yaml >/run/#HOSTNAME#-logs.tar 2>/dev/null; exit 0']
+    #
+    # Both destinations are read from the environment so a test can point them at its own
+    # directory. The installer sets neither, so an install writes where it always did.
+    - ['sh', '-c', 'tar -c --ignore-failed-read --transform="s/^/#HOSTNAME#-logs\//" /var/crash /var/log/installer /tmp/pre-install.log /autoinstall.yaml >"${XCAT_ERROR_ARCHIVE:-/run/#HOSTNAME#-logs.tar}" 2>/dev/null; exit 0']
     - ['sh', '-c', 'tail -n 80 /var/log/installer/curtin-install.log >"${XCAT_ERROR_CONSOLE:-/dev/console}" 2>/dev/null; exit 0']