Fix detection of installed_version

Ubuntu 12.04 LTS
GNU Awk 3.1.8

~# echo $(/opt/vagrant_ruby/bin/chef-solo --v | awk "{print \\\$2}" || "")
awk: {print \\}
awk:        ^ backslash not last character on line


~# echo $(/opt/vagrant_ruby/bin/chef-solo --v | awk "{print \$2}" || "")
10.14.2