slapos-testing: fix the way of *extending* $PATH

this is not possible with ENVIRONMENT=

software/slapos-testing/buildout.hash.cfg

@@ -16,5 +16,5 @@
 
 [template]
 filename = instance.cfg
-md5sum = f1a0eb06e8d1ea4fe6357bfedf5f0e54
+md5sum = 6b10e1a98e9da1f579cc9d423228c15b
 

software/slapos-testing/instance.cfg

@@ -63,12 +63,10 @@ repository = ${slapos.toolbox-repository:location}
 recipe = slapos.cookbook:wrapper
 wrapper-path = $${create-directory:bin}/runTestSuite
 command-line =
-   ${buildout:bin-directory}/runTestSuite
+   PATH=${coreutils:location}/bin:${curl:location}/bin:${openssl:location}/bin:${git:location}/bin:${libxslt:location}/bin:$PATH ${buildout:bin-directory}/runTestSuite
    --python_interpreter=${buildout:bin-directory}/${eggs:interpreter}
    --source_code_path_list=$${caucase:location},$${erp5.util:location},$${slapos.cookbook:location},$${slapos.core:location},$${slapos.recipe.build:location},$${slapos.recipe.cmmi:location},$${slapos.recipe.template:location},$${slapos.toolbox:location}
 parameters-extra = true
-environment =
-  PATH=${coreutils:location}/bin:${curl:location}/bin:${openssl:location}/bin:${git:location}/bin:${libxslt:location}/bin:$PATH
 
 [phantomjs-wrapper]
 recipe = slapos.cookbook:wrapper