Reduce exported profile

[imobachgs]

This PR adds support to determine the default start_mode for a system service.

require "yast2/system_service"
cups = Yast2::SystemService.find("cups")
cups.default_start_mode #=> :on_boot
cups.start_mode #=> :on_boot
cups.default_start_mode? #=> true

# Let's change cups start mode
cups.start_mode = :on_demand
cups.default_start_mode? #=> false

Trello: https://trello.com/c/1RXM7d8u/1851-8-reduce-profile-i-do-not-export-not-relevant-information
Bug: https://bugzilla.opensuse.org/show_bug.cgi?id=1172749

[coveralls]

Coverage increased (+0.02%) to 31.718% when pulling 813a315 on reduce-exported-profile into 5902d44 on master.

[teclator]

LGTM

[yast-bot]

✔️ Public Jenkins job #214 successfully finished
✔️ Created OBS submit request #815487