Several tests: cd inside subshell instead of around

Fixed all places where it was a straightforward change from cd'ing into a
directory and back via "cd .." to a cd inside a subshell.

Found these places with "git grep -w "cd \.\.".

Signed-off-by: Jens Lehmann <Jens.Lehmann@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t9123-git-svn-rebuild-with-rewriteroot.sh

@@ -8,10 +8,10 @@ test_description='git svn respects rewriteRoot during rebuild'
 . ./lib-git-svn.sh
 
 mkdir import
-cd import
+(cd import
 	touch foo
 	svn_cmd import -m 'import for git svn' . "$svnrepo" >/dev/null
-cd ..
+)
 rm -rf import
 
 test_expect_success 'init, fetch and checkout repository' '