Delete leftover data not associated to any institution (Bug 1314440)

Another patch for bug 1314440 makes it so that when you delete an
institution, this data gets deleted. This patch cleans up the data
for institutions that were deleted before that patch was merged.

Change-Id: I167001f444a3fd204b12610ca10274d6218d9f96
Signed-off-by: Son Nguyen <son.nguyen@catalyst.net.nz>