[backend] compatibility with 2.8 worker

Support 'registerserver' attribute when 2.8 worker sends its state.
Without this change, when a 2.8 worker sends its state, the following
message is logged in rep_server.log:

'unknown attribute: registerserver'

This 'registerserver' attribute was introduced in 2.8 commit 4e821a3d.

Bad code copied from the build package. Sigh.

found and fixed by Srinidhi B S

we will support LDAP mode once someone wrote testcases for it...
(but SUSE does not need the mode atm)

ruby-ldap returns true otherwise

[api] Fix error handling when extracting user info from LDAP.

Revert package webui fix 2.6

verify that correct revision is reverted after accepting request

verify that correct revision is reverted after accepting request

related to changes in PackageController:submit_request

add missing revision parameter to request

[webui] ignore lock status when checking user access rights for project

this enables e.g. unlocking project via webui

Update ReleaseNotes-2.6.10

Fix and test copy project operation

Backport ef268199 from master

Backport of master e03653b9

most lines are rubocop pacifiers though

* check that the source project is not building as prerequiste
* inject also x86_64 build results to source project

This will also check that copy project meta and build results are copied correctly.

regression from backport

[backend]Projectcopy backport2.6

Thanks @kaltsi 

Backport for 2.6 of Michael's fix for issue #1608