Combine two helper functions (one to check that a filesystem is opened, one to check that it isn't) into a single one that does both based on a boolean expectation flag.
NOTE: This changes the test when 'expect_open' is set to examine svn_fs_t->fsap_data instead of svn_fs_t->path (since that's what is checked when 'expect_open' is not set, too). I think that's fine, but wanted to note that here anyway just in case it rings some alarm in another developer's mind.
* subversion/libsvn_fs_base/fs.c (check_already_open): Removed as unused. (base_bdb_set_errcall): Update call to svn_fs__check_fs(). (open_databases): Use svn_fs__check_fs() instead of check_already_open().
* subversion/libsvn_fs_fs/fs.c (check_already_open): Removed as unused. (fs_create): Use svn_fs__check_fs() instead of check_already_open().