Ruby plugins: apply code changes as suggested by "rubocop --auto-correct"

plugins/thin/thins_peak_memory

@@ -33,20 +33,18 @@ You should have received a copy of the GNU General Public License along
 with this program; if not, write to the Free Software Foundation, Inc.,
 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
-
 #%# family=auto
 #%# capabilities=autoconf
 
 =end
 
-
 module Munin
   class ThinPeakMemory
     def run
-      instances = get_pids()
+      instances = get_pids
       instances.each do |instance|
-        pid, port = instance.split("|")
-        hwm = (pid_hwm(pid).to_i) / 1024
+        pid, port = instance.split('|')
+        hwm = pid_hwm(pid).to_i / 1024
         puts "thin_#{port}.value #{hwm}"
       end
     end
@@ -59,10 +57,10 @@ module Munin
     #      so the whole unix gang is happy ;)
     def pid_hwm(pid)
       res = `grep "VmHWM" /proc/#{pid}/status`.split[1]
-      if res.match("cannot access")
-        return nil
+      if res.match('cannot access')
+        nil
       else
-        return res
+        res
       end
     end
 
@@ -72,7 +70,7 @@ module Munin
     end
 
     def autoconf
-      get_pids().length > 0
+      get_pids.length > 0
     end
   end
 end
@@ -80,26 +78,26 @@ end
 mpm = Munin::ThinPeakMemory.new
 
 case ARGV[0]
-when "config"
-  puts "graph_title Thin Peak Memory (High Water Mark)"
-  puts "graph_vlabel HWM"
-  puts "graph_category webserver"
-  puts "graph_args -l 0"
-  puts "graph_scale yes"
-  puts "graph_info Tracks the peak memory of thin processes, aka High Water Mark."
+when 'config'
+  puts 'graph_title Thin Peak Memory (High Water Mark)'
+  puts 'graph_vlabel HWM'
+  puts 'graph_category webserver'
+  puts 'graph_args -l 0'
+  puts 'graph_scale yes'
+  puts 'graph_info Tracks the peak memory of thin processes, aka High Water Mark.'
   mpm.get_pids.each do |instance|
-    pid, port = instance.split("|")
+    pid, port = instance.split('|')
     puts "thin_#{port}.label thin_#{port}"
     puts "thin_#{port}.info Peak Memory"
     puts "thin_#{port}.type GAUGE"
     puts "thin_#{port}.min 0"
   end
-when "autoconf"
+when 'autoconf'
   if mpm.autoconf
-    puts "yes"
+    puts 'yes'
     exit 0
   end
-  puts "no"
+  puts 'no'
   exit 0
 else
   mpm.run