[feat] Revert "Removing develop-eggs/ directory before bootstrapping."

In SlapOS, bootstrap is called each time software release is invoked and
we do not want to delete develop-eggs directory.

This reverts commit 55d76b34.

src/zc/buildout/buildout.py

@@ -588,12 +588,6 @@ class Buildout(DictMixin):
     def bootstrap(self, args):
         __doing__ = 'Bootstrapping.'
 
-        if os.path.exists(self['buildout']['develop-eggs-directory']):
-            if os.path.isdir(self['buildout']['develop-eggs-directory']):
-                rmtree(self['buildout']['develop-eggs-directory'])
-                self._logger.debug(
-                    "Removed existing develop-eggs directory")
-
         self._setup_directories()
 
         # Install buildout and dependent eggs following pinned versions.

src/zc/buildout/tests/buildout.txt

@@ -3234,7 +3234,6 @@ or paths to use::
     >>> remove('setup.cfg')
     >>> print_(system(buildout + ' -csetup.cfg init demo other ./src'), end='')
     Creating '/sample-bootstrapped/setup.cfg'.
-    Creating directory '/sample-bootstrapped/develop-eggs'.
     Getting distribution for 'zc.recipe.egg>=2.0.6'.
     Got zc.recipe.egg
     Installing py.
@@ -3293,7 +3292,6 @@ for us::
     >>> remove('setup.cfg')
     >>> print_(system(buildout + ' -csetup.cfg init demo other ./src'), end='')
     Creating '/sample-bootstrapped/setup.cfg'.
-    Creating directory '/sample-bootstrapped/develop-eggs'.
     Installing py.
     Generated script '/sample-bootstrapped/bin/demo'.
     Generated script '/sample-bootstrapped/bin/distutilsscript'.