Fixed apache pid already running error when container was restarted (#20)

apache/run

@@ -2,4 +2,7 @@
 
 # From https://github.com/smebberson/docker-alpine/tree/master/alpine-apache
 
+# avoid 'already pid is running' error
+rm -f /run/apache2/httpd.pid
+
 exec /usr/sbin/apachectl -DFOREGROUND;