Jeremy's manpath workaround breaks on Fedora

In Fedora, /usr/man and /usr/local/man do not exist. So far, so good,
100% LSB compliant, etc. But in such case Jeremy's workaround tries
to install into /usr/man, so builds fail.

Suggestion: keep 'share/man' as the normal path and only invoke the
workaround when it's needed.

Ironically, if you look at Jeremy's original review patch 1, it worked
properly: it detected if something was symlinked and expanded those.
But then some kind of ridiculously involved problem with package
upgrades in Debian popped up and the condition was quietly inverted.
 See https://review.openstack.org/15146

Bug: 1073766
Change-Id: I78c2d2a0456ac2aa921b4d0720634622569d145d