Provide tags in perf-regression.run

A prior commit changed test-runner to enable tagging
of testgroups within a test suite runfile. They must
be specified in each runfile. Update the runfile for
performance regressions so it is properly tagged.

Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Closes #6830

tests/runfiles/perf-regression.run

@@ -22,9 +22,11 @@ timeout = 0
 post_user = root
 post = cleanup
 outputdir = /var/tmp/test_results
+tags = ['perf']
 
 [tests/perf/regression]
 tests = ['sequential_writes', 'sequential_reads', 'sequential_reads_cached',
     'sequential_reads_cached_clone', 'random_reads', 'random_writes',
     'random_readwrite']
 post =
+tags = ['perf', 'regression']