Fix the Apache vhost plugin

Fix bug in the Apache vhost plugin that prevented it from functioning.

Change V_MATCH_HOST to %v in custom access log format so the server name
is included in the log (V_MATCH_HOST is only available when using the
mod rewrite plugin).

Bug 1058849
Merge pull request #4656 from aaronknister/rhbz_1058849

Fix the Apache vhost plugin