Call pyuno.private_initTestEnvironment() only once

...instead of once for each class derived from CollectionsTestBase (as listed in
pyuno/PythonTest_pyuno_pytests_testcollections.mk), causing the

  assert(!pSVData->maDeInitHook.IsSet());

in Application::setDeInitHook (vcl/source/app/svapp.cxx) to fire.

This is probably far from being idiomatic Python code...

Change-Id: I8cd1470c085b16b7b82468a308cfd1dead2db034
diff --git a/pyuno/qa/pytests/testcollections_base.py b/pyuno/qa/pytests/testcollections_base.py
index b3fcd2e..d3e8068 100644
--- a/pyuno/qa/pytests/testcollections_base.py
+++ b/pyuno/qa/pytests/testcollections_base.py
@@ -13,13 +13,17 @@ import uno
from org.libreoffice.unotest import pyuno
from com.sun.star.beans import PropertyValue

testEnvironmentInitialized = False

class CollectionsTestBase(unittest.TestCase):

    @classmethod
    def setUpClass(cls):
        cls.context = pyuno.getComponentContext()
        pyuno.private_initTestEnvironment()
        global testEnvironmentInitialized
        if not testEnvironmentInitialized:
            pyuno.private_initTestEnvironment()
            testEnvironmentInitialized = True

    def setUp(self):
        self._components = []