(maint) Remove ext/rack/README reference from debian/rules

In a previous commit, files in ext/rack/files were moved up a directory to
ext/rack and some unneeded files were removed. Among the removed files was
README, which was unfortunately still used in the debian/rules file as a
supplemental doc for the puppetmaster-passenger package. The lack of
ext/rack/README caused the rules evaluation to fail, which caused debian
packaging to fail. This commit addresses that by removing the README references
from the debian/rules file.
Merge pull request #2070 from haus/maint/stable/fix_rules_for_missing_readme

(maint) Remove ext/rack/README reference from debian/rules
(maint) Rename expected apache vhost in debian/rules

In a previous commit, files in ext/rack/files were moved up a directory to
ext/rack and some files were renamed. Among the renamed files was
apache2.conf, which was renamed to example-passenger-vhost.conf.  This caused
the rules evaluation to fail, which caused debian packaging to fail. This
commit addresses that by renaming the vhost references in the debian/rules
file.
Merge pull request #2071 from haus/maint/stable/fix_rules_for_renamed_vhost

(maint) Rename expected apache vhost in debian/rules