Fix in custom fact "apache_version" for RHEL.

[BobVincentatNCRdotcom]

The custom fact defined by lib/facter/apache_version.rb runs
"apachectl -v" and applies the following regular expression:

^Server version: Apache\/([\w\.]+) \(([\w]+)\)

On RHEL 7.1, running apachectl -v produces the following output:

Server version: Apache/2.4.6 (Red Hat Enterprise Linux)

The regex fails to match the output because it does not allow
for whitespace inside the parentheses. The following modified
regex matches properly:

^Server version: Apache\/([\w\.]+) \(([\w ]+)\)

[BobVincentatNCRdotcom]

For easy googling, the error shown on puppet runs without this patch is as follows:

Error: Facter: error while resolving custom fact "apache_version": undefined method `[]' for nil:NilClass