FCREPO-1073: Use latest Akubra (akubra-fs bugfixes)
FCREPO-1073: Use latest Akubra (akubra-fs bugfixes)

Updates Akubra version to 0.4.0

https://jira.duraspace.org/browse/FCREPO-1073
andreasnef/fcrepo,andreasnef/fcrepo,fcrepo3/fcrepo,andreasnef/fcrepo,fcrepo3/fcrepo,fcrepo3/fcrepo,fcrepo3/fcrepo,andreasnef/fcrepo