Fix some issues reported by lintian

Fix some issues reported by lintian

• Use secure copyright file specification URI. (insecure-copyright-format-uri)
• Depend on newer debhelper (>= 9.20160709) rather than dh-systemd. (build-depends-on-obsolete-package)
• Bump debhelper dependency to >= 10, since that's what is used in debian/compat. (package-lacks-versioned-build-depends-on-debhelper)
• Remove unnecessary 'Testsuite: autopkgtest' header. (unnecessary-testsuite-autopkgtest-field)
• Set upstream metadata fields: Bug-Database, Bug-Submit, Repository, Repository-Browse. (upstream-metadata-file-is-missing, upstream-metadata-missing-bug-tracking, upstream-metadata-missing-repository)
• Update Vcs-* headers from vcswatch. (vcs-obsolete-in-debian-infrastructure)
• Use canonical URL in Vcs-Browser. (vcs-field-not-canonical)
• Drop unnecessary dh arguments: --with=systemd (debian-rules-uses-unnecessary-dh-argument)

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The bot will automatically update the merge proposal to resolve merge conflicts or close the merge proposal when all changes are applied through other means (e.g. cherry-picks). Updates may take several hours to propagate.

Build and test logs for this branch can be found at https://janitor.debian.net/lintian-fixes/pkg/open-isns/d4691960-e84c-452d-b4ee-8716174748f8.

These changes have no impact on the binary debdiff.

You can also view the diffoscope diff (unfiltered).