monitor: use monitor- prefix in cert and key

By using a short filenames like "httpd.crt" or "httpd.key", we risk have
conflict with users of this stack. Use a name with more context, that
should likely not be used by applications.

This solves an issue with lamp stack, that was visible with nextcloud
software:

     While:
       Installing ca-apache-php.
     Error: The following paths are already installed by other sections: {'/srv/slapgrid/slappart8/srv/testnode/cvt/inst/test0-0/tmp/inst/ncs2/srv/ssl/certs/httpd.key': 'ca-monitor-httpd', '/srv/slapgrid/slappart8/srv/testnode/cvt/inst/test0-0/tmp/inst/ncs2/srv/ssl/certs/httpd.crt': 'ca-monitor-httpd'}

stack/monitor/buildout.hash.cfg

@@ -14,7 +14,7 @@
 # not need these here).
 [monitor2-template]
 filename = instance-monitor.cfg.jinja2.in
-md5sum = e1c7d1c21a942064e2f3f40463b10177
+md5sum = 84bc2cf29e34b48c51116d93e2be7636
 
 [monitor-httpd-conf]
 _update_hash_filename_ = templates/monitor-httpd.conf.in

stack/monitor/instance-monitor.cfg.jinja2.in

@@ -165,8 +165,8 @@ port = ${monitor-instance-parameter:monitor-httpd-port}
 pid-file = ${directory:run}/monitor-httpd.pid
 access-log = ${directory:log}/monitor-httpd-access.log
 error-log = ${directory:log}/monitor-httpd-error.log
-cert-file = ${ca-directory:certs}/httpd.crt
-key-file = ${ca-directory:certs}/httpd.key
+cert-file = ${ca-directory:certs}/monitor-httpd.crt
+key-file = ${ca-directory:certs}/monitor-httpd.key
 htpasswd-file = ${httpd-monitor-htpasswd:htpasswd-path}
 url = https://[${monitor-instance-parameter:monitor-httpd-ipv6}]:${:port}
 httpd-cors-config-file = ${monitor-httpd-cors:rendered}
@@ -194,8 +194,8 @@ recipe = slapos.cookbook:wrapper
 command-line = {{ apache_location }}/bin/httpd -f ${monitor-httpd-conf:rendered} -DFOREGROUND
 wrapper-path = ${directory:bin}/monitor-httpd
 wait-for-files =
-  ${ca-directory:certs}/httpd.key
-  ${ca-directory:certs}/httpd.crt
+  ${monitor-httpd-conf-parameter:key-file}
+  ${monitor-httpd-conf-parameter:cert-file}
   ${monitor-httpd-graceful-wrapper:rendered}
 
 [monitor-httpd-graceful-wrapper]