slapos-sr-testing: do not end paths with /

This may lead to weird like ...//... or worse: here, the [gcc] part of
the tested SR will do "os.path.dirname('/usr/bin/')" (when using system
gcc), causing ${gcc:prefix} to be invalid ('/usr/bin' instead of '/usr')
and most sharable parts will rebuild (different [gcc] signature).

software/slapos-sr-testing/buildout.hash.cfg

@@ -15,4 +15,4 @@
 
 [template]
 filename = instance.cfg
-md5sum = 9639d0c0e161c094454808fb95fc9781
+md5sum = 5ba23849f0b9bcfbe2534314ce7f48e8

software/slapos-sr-testing/instance.cfg

@@ -36,7 +36,7 @@ nxdtest-working-dir = ${:var}/nxdtest
 recipe = slapos.recipe.template:jinja2
 rendered = ${directory:etc}/${:_buildout_section_name_}
 template = inline:
-  export PATH={{ buildout['bin-directory'] }}:{{ curl_location }}/bin/:{{ faketime_location }}/bin/:{{ openssl_location }}/bin/:/usr/bin/:/bin
+  export PATH={{ buildout['bin-directory'] }}:{{ curl_location }}/bin:{{ faketime_location }}/bin:{{ openssl_location }}/bin:/usr/bin:/bin
   export SLAPOS_TEST_IPV4=${slap-configuration:ipv4-random}
   export SLAPOS_TEST_IPV6=${slap-configuration:ipv6-random}
   export SLAPOS_TEST_WORKING_DIR=${directory:test-working-dir}