dbscripts: Ensure atomicity of lastsync file

We try to ensure an atomic operation of the lastsync file. This requires creating a tmp file which needs to be ignored.
This should take care of having empty lastsync files being served.
Possible cause is that the IO is stuck thus taking several seconds to write the lastsync timestamp.
This causes mirrors to download the empty file which causes checks to fail.

roles/dbscripts/files/lastsync.service

@@ -3,5 +3,5 @@ Description=lastsync
 
 [Service]
 Type=oneshot
-User=ftp
-ExecStart=/usr/bin/bash -c "date +%%s > /srv/ftp/lastsync"
+ExecStart=/usr/bin/bash -c "date +%%s > /srv/ftp/lastsync.tmp && \
+    mv /srv/ftp/lastsync.tmp /srv/ftp/lastsync"

roles/dbscripts/templates/rsyncd.conf.proto.j2

@@ -30,19 +30,19 @@ hosts deny = *
 [ftp]
 	path = /srv/ftp
 	comment = ftp area (most mirrors should use this)
-	exclude = /archive/ /other/ /sources/ /*-debug/ /pool/*-debug/
+	exclude = /archive/ /other/ /sources/ /*-debug/ /pool/*-debug/ /lastsync.tmp
 
 [ftp_tier1]
 	path = /srv/ftp
 	comment = ftp area (most mirrors should use this)
-	exclude = /archive/ /other/ /sources/ /*-debug/ /pool/*-debug/
+	exclude = /archive/ /other/ /sources/ /*-debug/ /pool/*-debug/ /lastsync.tmp
 	hosts allow = @@ALLOWHOSTS_TIER1@@
 	max connections = 0
 
 [ftp_auth]
 	path = /srv/ftp
 	comment = ftp area, passworded (same as 'ftp')
-	exclude = /archive/ /other/ /sources/ /*-debug/ /pool/*-debug/
+	exclude = /archive/ /other/ /sources/ /*-debug/ /pool/*-debug/ /lastsync.tmp
 	hosts allow = *
 	auth users = *
 	secrets file = /etc/rsyncd.secrets
@@ -52,19 +52,19 @@ hosts deny = *
 [ftpfull]
 	path = /srv/ftp
 	comment = ftp area (everything, including very old versions, except sources)
-	exclude = /sources/
+	exclude = /sources/ /lastsync.tmp
 
 [ftpfull_tier1]
 	path = /srv/ftp
 	comment = ftp area (everything, including very old versions, except sources)
-	exclude = /sources/
+	exclude = /sources/ /lastsync.tmp
 	hosts allow = @@ALLOWHOSTS_TIER1@@
 	max connections = 0
 
 [ftpfull_auth]
 	path = /srv/ftp
 	comment = ftp area (everything, including very old versions, except sources)
-	exclude = /sources/
+	exclude = /sources/ /lastsync.tmp
 	hosts allow = *
 	auth users = *
 	secrets file = /etc/rsyncd.secrets
@@ -74,17 +74,20 @@ hosts deny = *
 [kitchensink]
 	path = /srv/ftp
 	comment = ftp area (everything, including very old versions)
+	exclude = /lastsync.tmp
 	hosts allow = {{ hostvars['archlinux.org']['ipv4_address'] }} {{ hostvars['archlinux.org']['ipv6_address'] }}
 
 [kitchensink_tier1]
 	path = /srv/ftp
 	comment = ftp area (everything, including very old versions)
+	exclude = /lastsync.tmp
 	hosts allow = @@ALLOWHOSTS_TIER1@@ {{ hostvars['gemini.archlinux.org']['ipv4_address'] }} {{ hostvars['gemini.archlinux.org']['ipv6_address'] }} {{ hostvars['repos.archlinux.org']['ipv4_address'] }} {{ hostvars['repos.archlinux.org']['ipv6_address'] }}
 	max connections = 0
 
 [kitchensink_auth]
 	path = /srv/ftp
 	comment = ftp area (everything, including very old versions)
+	exclude = /lastsync.tmp
 	hosts allow = *
 	auth users = *
 	secrets file = /etc/rsyncd.secrets