Install slapos.libnetworkcache in test.

By the way revert "Revert "Revert "Allow to find slapos.libnetworkcache during
test.""" (commit 0fbf2ccf ), as it is not
required anymore.

src/zc/buildout/networkcache.txt

 Using buildout with cache over network
 ======================================
 
+Pure buildout ignore networkcache:
+
+   >>> write(sample_buildout, 'buildout.cfg',
+   ... '''
+   ... [buildout]
+   ... parts =
+   ... networkcache-section = networkcache
+   ... ''')
+   >>> print system(buildout)
+   Unused options for buildout: 'networkcache-section'.
+
+So lets activate networkcache in buildout:
+   >>> write(sample_buildout, 'buildout.cfg',
+   ... '''
+   ... [buildout]
+   ... parts = networkcache
+   ... find-links =
+   ...   http://pypi.python.org/pypi/slapos.libnetworkcache
+   ...   http://chandlerproject.org/bin/view/Projects/MeTooCrypto
+   ... # Do not register this buildout run
+   ... installed =
+   ...
+   ... [networkcache]
+   ... recipe = zc.recipe.egg
+   ... eggs =
+   ...   slapos.libnetworkcache
+   ...   zc.buildout
+   ... ''')
+   >>> ignore = system(buildout)
+
+Now let's prepare networkcache server:
    >>> nc_data = tmpdir('nc_data')
    >>> nc_url = start_nc(nc_data)
 

src/zc/buildout/testing.py

@@ -270,7 +270,7 @@ def make_buildout(executable=None):
     """Make a buildout that uses this version of zc.buildout."""
     # Create a basic buildout.cfg to avoid a warning from buildout.
     open('buildout.cfg', 'w').write(
-        "[buildout]\nparts =\nfind-links = http://pypi.python.org/pypi/slapos.libnetworkcache"
+        "[buildout]\nparts =\n"
         )
     # Get state of installer defaults so we can reinstate them (instantiating
     # a Buildout will force the Buildout's defaults on the installer).