Change nfsiostat source to url to ensure it is cached (#457)

* Change git source to url to ensure it is cached

* Apply suggestions from code review

Co-authored-by: Kylian Serrania <kylian.serrania@datadoghq.com>

* Change default version

---------

Co-authored-by: Kylian Serrania <kylian.serrania@datadoghq.com>

Author: KevinFairise2

config/software/nfsiostat.rb

@@ -16,11 +16,13 @@
 #
 
 name "nfsiostat"
-default_version "nfs-utils-2-1-1"
+default_version "2.1.1"
 
-source git: "git://git.linux-nfs.org/projects/steved/nfs-utils.git"
+source url: "https://mirrors.edge.kernel.org/pub/linux/utils/nfs-utils/#{version}/nfs-utils-#{version}.tar.gz",
+       sha256: "381bb3f6aa4b314538db0bcfb242da855c2eb36e2059cf61aa498c0220684363",
+       extract: :seven_zip
 
-relative_path "nfs-utils"
+relative_path "nfs-utils-#{version}"
 
 build do
   license "GPL-2.0"