maint: test: polish live_test.sh

• from issues found with ShellCheck, fix those marked as important
• suppress some ShellCheck issues, mostly related to the fact that some ticket-related variables are established dynamically, also drop a never-used local variable (see commits 74a3f5c + 4136682) and another global one that was used but consequently ditched (see commits 08f56bd + d952b27)
• fix s/boots not uptodate/booths not up-to-date/ spelling
• fix whitespace issues

Signed-off-by: Jan Pokorný <jpokorny@redhat.com>