test-dispatch: stabilize the test When cwd is removed and `hg` is executed, some shells may run `getcwd` before forking and executing, some may not do it, some may print a different error message. The test should be shell-independent so let's just avoid checking the error message. Differential Revision: https://phab.mercurial-scm.org/D1282

local test passed
addgroupcopy test passed
clone test passed
lowlevelcopy test passed