Code review comment for lp:~stub/charms/trusty/cassandra/spike

Another run at http://reports.vapour.ws/charm-test-details/charm-bundle-test-parent-263

http://reports.vapour.ws/all-bundle-and-charm-results/charm-bundle-test-parent-263/charm/charm-testing-hp/3 shows test_external_mount failing at 11:07, when amulet fails to read the contents of a remote directory. However, http://data.vapour.ws/charm-test/charm-bundle-test-hp-120-all-machines-log clearly shows the directory being created at 11:04:34 (the migration starts at 11:04:29).