tests: make directory to prevent test process from going out of $TESTTMP Before this patch, test process for test-bookmarks.t goes out of $TESTTMP at "cd .." before creation of "orderrepo" repository. To prevent test process from going out of $TESTTMP, this patch makes directory "repo" sub-directory and executes almost all test scenarios in test-bookmarks.t under it. This is preparation for new test added in subsequent patch.