Revert "(FACT-658) facter doesn't parse gnu uptime output"

This reverts commit b8ea20db6826c906f9c527a7dbf9aa04fbfae960.

After some discussion with Josh Cooper, we agreed that relying
on the exact path to uptime for all platforms is the wrong approach,
so we're reverting.

Two possibilities are:
1) Set the exact path to uptime for Solaris only
2) Make the uptime parsing resilient to gnu uptime output
(FACT-658) Update uptime regexes for Solaris edge cases

In some versions of `uptime` on some versions of Solaris,
output may differ from what we previously expected. Specifically,
the coreutils GNU version does not include a ',' after 'day(s)', and
in some cases uptime may return a '-' character in the minutes field.

This commit updates the relevant regular expressions so that we can
match and parse these uptime strings.
Merge pull request #816 from whopper/FACT-658/solaris-gnu-uptime

(FACT-658) Update uptime regexes for Solaris edge cases
(maint) Fix preserve_hosts usage

Rakefile wasn't updated for new preserve_hosts beaker options. Updates
it to match puppet.
Merge pull request #819 from MikaelSmith/maint/stable/fix-preserved-hosts

(maint) Fix preserve_hosts usage
Merge remote-tracking branch 'upstream/stable'

* upstream/stable:
  (maint) Fix preserve_hosts usage
  (FACT-658) Update uptime regexes for Solaris edge cases
  Revert "(FACT-658) facter doesn't parse gnu uptime output"
(FACT-755) Fix unprivileged Xen detection when /proc/xen is not present.

/dev/xvda1 exists on virtual hosts on physical xen hosts. Therefore use xenu as
virtual, so is_virtual is also true. Otherwise it is false.
So we can merge /proc/xen and /dev/xvda1
Merge pull request #812 from chiemseesurfer/master

(FACT-755) Fix unprivileged Xen detection when /proc/xen is not present.