Apidoc: multiple "Could not generate doc" warnings

Current Carbon CSIT (all job) generate this in karaf.log [0]:

2017-09-29 12:32:32,667 | INFO | qtp532498781-647 | BaseYangSwaggerGenerator | 375 - org.opendaylight.netconf.sal-rest-docgen - 1.5.2.Carbon | Modules found [453]
2017-09-29 12:32:32,668 | WARN | qtp532498781-647 | BaseYangSwaggerGenerator | 375 - org.opendaylight.netconf.sal-rest-docgen - 1.5.2.Carbon | Could not generate doc for IANAifType-MIB,2010-02-11

Such warnings are present for 268 of 453 modules.
Not sure if the modules are somewhat wrong, or there is an apidocs bug (perhaps both).

Marking as a Bug, because the rest call sometimes take longer [1] than 15 seconds, the warnings might be the reason why it takes so long.

[0] https://logs.opendaylight.org/releng/jenkins092/netconf-csit-1node-userfeatures-all-carbon/418/odl1_karaf.log.gz
[1] https://logs.opendaylight.org/releng/jenkins092/netconf-csit-1node-userfeatures-all-carbon/419/log.html.gz#s1-s2-s1-t1-k1-k1-k3-k3-k1