Fix missing 'should' in rspecs

W/o this fix, rspec tests will continue
report false positives for many test cases
with config_file involved allowing even
more regressions to be accepted and merged
in master branch.

Fix contains missing 'should' and multiline
regex (/.*/m) statements.

Note: Perhaps, this fix should be merged
despite on CI failure. The failure is natural
for this specific case only, due to multiple
regressions had been accepted while tests
were reporting false positives results.
And in order to fix failing tests later, all
of these regressions should be assdessed by
other patches as well.

Closes-bug: #MODULES-1416

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>