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

tests/test-dispatch.t

@@ -68,9 +68,13 b' Current directory removed:'
   $ mkdir $TESTTMP/repo1
   $ cd $TESTTMP/repo1
   $ rm -rf $TESTTMP/repo1
-  $ HGDEMANDIMPORT=disable hg version -q
-  abort: error getting current working directory: * (glob) (no-chg !)
-  chg: abort: failed to getcwd (errno = *) (glob) (chg !)
-  [255]
+
+The output could be one of the following and something else:
+ chg: abort: failed to getcwd (errno = *) (glob)
+ abort: error getting current working directory: * (glob)
+ sh: 0: getcwd() failed: No such file or directory
+Since the exact behavior depends on the shell, only check it returns non-zero.
+  $ HGDEMANDIMPORT=disable hg version -q 2>/dev/null || false
+  [1]
 
 #endif