gerrit, master builds: use ASCIIDOC_WARNINGS_CHECK

The asciidoc warnings check fails the build if asciidoc prints a warning
while building the documentation. We had this enabled by default, but
since OBS uses various asciidoc versions, we could get unexpected build
failures (different asciidoc versions print different warnings).

Now that it is disabled by default, explicitly enable it for jenkins
again.

Related: OS#4140
Depends: Iac993a0d1b17205397a1f1ef1a7bd3f9df739e36 (osmo-gsm-manuals)
Change-Id: I8775d45b4dc1a5a46e2ba042fc7ee7d9f10f18cc
2 files changed