subrepo: fix hgrc paths section during subrepo pulling

There are two bugs in current subrepo ctor:
 - hgrc paths were using parent repo (ctx._repo) instead of self._repo
 - it was joined with local extract path, not its source repo path

Fixed both bugs using _abssource on self once it is fully initialized.
It gets the job done perfectly for pull and push urls.

mercurial/subrepo.py

@@ -193,8 +193,11 b' class hgsubrepo(object):'
                 fp.write('%s = %s\n' % (key, value))
                 self._repo.ui.setconfig('paths', key, value)
 
-            defpath = os.path.join(_abssource(ctx._repo), path)
+            defpath = _abssource(self._repo)
+            defpushpath = _abssource(self._repo, True)
             addpathconfig('default', defpath)
+            if defpath != defpushpath:
+                addpathconfig('default-push', defpushpath)
             fp.close()
 
     def dirty(self):

tests/test-subrepo.out

@@ -263,6 +263,6 b' committing subrepository nested_absolute'
 updating to branch default
 2 files updated, 0 files merged, 0 files removed, 0 files unresolved
 [paths]
-default = $HGTMP/test-subrepo/sub/mercurial/main/nested_absolute
+default = $HGTMP/test-subrepo/sub/mercurial/nested_absolute
 [paths]
-default = $HGTMP/test-subrepo/sub/mercurial/main/nested_relative
+default = $HGTMP/test-subrepo/sub/mercurial/main/../nested_relative