tests: don't rely on 'false' exit code in test-run-tests.t
On Solaris:
$ sh -c 'false ; echo $?'
255
$ rm -rf a $ hg init a $ cd a $ echo a > a $ hg ci -Am0 adding a $ hg tag t1 # 1 $ hg tag --remove t1 # 2 $ hg co 1 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg tag -f -r0 t1 $ hg tags tip 3:a49829c4fc11 t1 0:f7b1eb17ad24