Arycd: test_shell - sync with loop_test

Update the 'test_shell.sh' using the more recent 'loop_test.sh' so that
it now exercises the 'repo-snoop-url' path.

Test Plan: $ ./testbed/arcyd/test_shell.sh
Arcyd: fix phlurl_watcher refresh hash comparison

Hash comparisons should be via some representation that supports
comparison - apparently by default the hash object comparison is 'is'
instead of 'is equal to'.

Fix the comparison in phlurl_watcher so that repos aren't automatically
considered as changed on every refresh.

Test Plan:
$ ./precommit.sh
$ ./testbed/arcyd/acceptance_tests.sh
$ ./testbed/arcyd/test_loop.sh
  - manually inspect reviews to make sure repo updates
$ ./testbed/arcyd/test_shell.sh
  - manually interact with phlurl_watcher to ensure it doesn't report
    changes whenever refresh() is called.