tests: use %TESTNUMBER instead of fixed number

This makes the tests easier to copy and relocate to other test numbers
without having to update content.

Closes #6738

tests/data/test503

@@ -48,7 +48,7 @@ http-proxy
 </server>
 # tool is what to use instead of 'curl'
 <tool>
-lib503
+lib%TESTNUMBER
 </tool>
 <features>
 proxy
@@ -57,9 +57,9 @@ proxy
 simple multi http:// through proxytunnel with authentication info
  </name>
  <command>
-http://machine.503:%HTTPPORT/503 %HOSTIP:%PROXYPORT
+http://machine.%TESTNUMBER:%HTTPPORT/%TESTNUMBER %HOSTIP:%PROXYPORT
 </command>
-<file name="log/test503.txt">
+<file name="log/test%TESTNUMBER.txt">
 foo
    bar
 bar
@@ -71,15 +71,15 @@ moo
 # Verify data after the test has been "shot"
 <verify>
 <proxy>
-CONNECT machine.503:%HTTPPORT HTTP/1.1
-Host: machine.503:%HTTPPORT
+CONNECT machine.%TESTNUMBER:%HTTPPORT HTTP/1.1
+Host: machine.%TESTNUMBER:%HTTPPORT
 Proxy-Authorization: Basic dGVzdDppbmc=
 Proxy-Connection: Keep-Alive
 
 </proxy>
 <protocol>
-GET /503 HTTP/1.1
-Host: machine.503:%HTTPPORT
+GET /%TESTNUMBER HTTP/1.1
+Host: machine.%TESTNUMBER:%HTTPPORT
 Authorization: Basic dGVzdDppbmc=
 Accept: */*