test/system: Silence SC2155

[debarshiray]

Otherwise https://www.shellcheck.net/ would complain:

  Line 624:
  local system_id="$(get_system_id)"
        ^-------^ SC2155 (warning): Declare and assign separately to
                  avoid masking return values.

See: https://www.shellcheck.net/wiki/SC2155

[softwarefactory-project-zuul[bot]]

Build failed. https://softwarefactory-project.io/zuul/t/local/buildset/4ad50e93e98f4449ae2ac5daf4f48086

:heavy_check_mark: unit-test SUCCESS in 9m 08s :heavy_check_mark: unit-test-migration-path-for-coreos-toolbox SUCCESS in 3m 24s :heavy_check_mark: unit-test-restricted SUCCESS in 7m 29s :x: system-test-fedora-rawhide FAILURE in 41m 13s :heavy_check_mark: system-test-fedora-38 SUCCESS in 33m 10s :heavy_check_mark: system-test-fedora-37 SUCCESS in 32m 21s

[debarshiray]

There are still some test failures on Fedora Rawhide. For example:

fedora-rawhide | not ok 3 help: Run command 'help' in 145ms
fedora-rawhide | # (from function `assert_line' in file test/system/libs/bats-assert/src/assert.bash, line 479,
fedora-rawhide | #  in test file test/system/002-help.bats, line 45)
fedora-rawhide | #   `assert_line --index 0 --partial "toolbox(1)"' failed
fedora-rawhide | # /usr/bin/man
fedora-rawhide | #
fedora-rawhide | # -- line does not contain substring --
fedora-rawhide | # index     : 0
fedora-rawhide | # substring : toolbox(1)
fedora-rawhide | # line      : troff:<standard input>:33: warning: cannot select font 'C'
fedora-rawhide | # --

I believe these are because of changes in various other components in Fedora 39, which we need to track down one by one and work out a fix.

In the mean time, I am going to temporarily override these failures.