base::os::debian: Correct regexp syntax in a systemd filter-syslog line

NEWS

+unreleased (TBD)
+
+    [os] Small fix in base::os::debian to one of the systemd-related 
+    syslog-filter regexes (akkornel)
+
 release/004.050 (2015-07-24)
 
     [rpm] Making available openafs-1.6.{7,8}-EL{5,6,7}.repo files 

files/os/etc/filter-syslog/debian

@@ -67,7 +67,7 @@ systemd: /^(?:Starting|Started) Session \d+ of user \w+\.$/
 systemd: /^(?:Created|Removed) slice user-\d+\.slice\.$/
 systemd: /^(?:Starting|Stopping) User Manager for UID \d+\.\.\.$/
 systemd: /^(?:Started|Stopped) User Manager for UID \d+\.$/
-systemd: /^(?:Starting|Stopping|Stopped) (?:target)? (?:Paths|Timers|Sockets|Basic System|Default|Shutdown)\.$/
+systemd: /^(?:Starting|Stopping|Stopped) (?:target )?(?:Paths|Timers|Sockets|Basic System|Default|Shutdown)\.$/
 systemd: /^Reached target (?:Paths|Timers|Sockets|Basic System|Default|Shutdown)\.$/
 systemd: /^Startup finished in \d+ms\.$/
 systemd-logind: /^New session [0-9a-f]+ of user \w+.$/