Port of a community contribution from @glensc to upstream.

In Ruby 2.4, `URI.join("http://test//", "a").to_s` will
remove the double slash, however it's not the case in
Ruby 2.5. Using chomp should work better for the intention,
as we're not trying to allow things like ../ or / paths
resolution.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/53180

Partially addresses #47424.

the ci status icons are generated client side, wo we don't need the
static files anymore.

Leaving a trailing slash in the context option causes the jira-ruby
gem to add an extra slash in HTTP requests to the URL, preventing
JIRA from working properly.

Closes #42494

Adds a rubocop rule (with autocorrect) to ensure line break after guard clauses.

Add OpenSSL::SSL::SSLError to rescue in JiraService & IssueTrackerService. This
will prevent an exception in production and instead display
a message to the user.

Use the EnforcedStyleForMultiline: no_comma option.
Signed-off-by: NRémy Coutable <remy@rymai.me>

Signed-off-by: NRémy Coutable <remy@rymai.me>