systemd: Clean up override files

Standardize on starting with the drop-in files with "10-" and dashes for
spaces.  Looks nice and allows for ordering the overrides.

manifests/base/distccd.pp

 class nest::base::distccd {
   if $::nest::distcc_server {
-    $disable_verbose_content = @(EOT)
-      [Service]
-      ExecStart=
-      ExecStart=/usr/bin/distccd --no-detach --daemon --port 3632 -N 15 --allow 0.0.0.0/0
-      | EOT
+    file { '/etc/systemd/system/distccd.service.d/00gentoo.conf':
+      ensure  => absent,
+    }
 
-    file { '/etc/systemd/system/distccd.service.d/10-nest.conf':
+    file { '/etc/systemd/system/distccd.service.d/10-allowed-servers.conf':
       mode    => '0644',
       owner   => 'root',
       group   => 'root',
-      content => $disable_verbose_content,
+      content => "[Service]\nEnvironment=\"ALLOWED_SERVERS=0.0.0.0/0\"\n",
       notify  => Nest::Lib::Systemd_reload['distccd'],
     }
 

manifests/base/fstab.pp

@@ -120,6 +120,10 @@ class nest::base::fstab {
     ;
 
     '/etc/systemd/system/var.mount.d/lazyunmount.conf':
+      ensure => absent,
+    ;
+
+    '/etc/systemd/system/var.mount.d/10-lazy-unmount.conf':
       content => $var_lazy_unmount,
       notify  => Nest::Lib::Systemd_reload['fstab'],
     ;

manifests/base/zfs.pp

@@ -21,6 +21,10 @@ class nest::base::zfs {
     ;
 
     '/etc/systemd/system/zfs-mount.service.d/load-key.conf':
+      ensure => absent,
+    ;
+
+    '/etc/systemd/system/zfs-mount.service.d/10-load-key.conf':
       content => $zfs_mount_override,
       notify  => Nest::Lib::Systemd_reload['zfs'],
     ;