slapos-testing: add libnetworkcache egg as dependency.

buildout can be run and may need libnetworkcache in order to run tests (if zc.buildout.testing.buildoutSetUp() is called).

software/slapos-testing/software.cfg

@@ -33,6 +33,7 @@ eggs =
   slapos.cookbook
   collective.recipe.template
   plone.recipe.command
+  slapos.libnetworkcache
 entry-points =
   runTestSuite=erp5.util.testsuite:runTestSuite
 scripts =
@@ -93,3 +94,4 @@ collective.recipe.template = 1.10
 plone.recipe.command = 1.1
 slapos.recipe.build = 0.12
 slapos.recipe.template = 2.5
+slapos.libnetworkcache = 0.14.1