Use context manager for file handling in some system modules. (#65227)

changelogs/fragments/65227.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - system_service - use a context manager for file handling.

lib/ansible/modules/service.py

@@ -385,7 +385,7 @@ class Service(object):
 
         self.changed = None
         entry = '%s="%s"\n' % (self.rcconf_key, self.rcconf_value)
-        RCFILE = open(self.rcconf_file, "r")
+        with open(self.rcconf_file, "r") as RCFILE:
             new_rc_conf = []
 
             # Build a list containing the possibly modified file.
@@ -407,9 +407,6 @@ class Service(object):
                 # Add line to the list.
                 new_rc_conf.append(rcline.strip() + '\n')
 
-        # We are done with reading the current rc.conf, close it.
-        RCFILE.close()
-
         # If we did not see any trace of our entry we need to add it.
         if self.changed is None:
             new_rc_conf.append(entry)