update flux dependencies and package (#2541)

* update flux dependencies and package

* refinements from @adamjstewart

* fix flux document generation

The docbook-xsl package has been added, and correctly configures catalog
files to generate documentation correctly with asciidoc.

var/spack/repos/builtin/packages/asciidoc/package.py

@@ -36,6 +36,8 @@ class Asciidoc(Package):
 
     depends_on('libxml2')
     depends_on('libxslt')
+    depends_on('docbook-xml')
+    depends_on('docbook-xsl')
 
     def install(self, spec, prefix):
         configure('--prefix=%s' % prefix)