When "All guides locked", newly created guides are unlocked till reopen.

Separated out from #687 (closed) (was not sure if this was intended behavior of the guides before).

Steps to reproduce:

• Open Inkscape
• Create some guides
• Press the lock button in the left left corner (intersection of the two rulers)
  • Note the guides are all locked
• Create new guides
  • Note new guides are not locked by default
• Save and reopen the file
  • Guides are now all locked

What happened?

• New guides are left unlocked

What should have happened?

• New guides are locked on creation if "Create all guides" is checked. Based off this commit (ed905044), new guides should have inkscape:locked set to true in this case too.

Inkscape Version and Operating System:

• 1.1-dev (31d2c027, 2020-04-13) Linux Mint 19.1
• 1.0rc1 (09960d6f, 2020-04-09) appimage Linux Mint 19.1
• Inkscape 0.92.5 (3444facdaf, 2020-04-14) Linux Mint 19.1

not replicated in 0.92.4 flatpak Linux Mint 19.1