Make FS tests cover svn_fs_txn_base_revision() as well.

* subversion/tests/libsvn_fs/fs-test.c
  (merging_commit): In two places where we start a transaction off a
                    revision other than HEAD, verify that we actually
                    picked the one we intended as a base.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1636482 13f79535-47bb-0310-9956-ffa450edef68
Follow-up to r1636478: Style change.  No functional change.

* subversion/libsvn_fs_fs/util.c
  (svn_fs_fs__path_txns_dir): Put the parantheses around the whole
                              conditional expression.

Suggested by: brane

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1636483 13f79535-47bb-0310-9956-ffa450edef68