Copier's cleanupFiles is independent from the Copier's KeyPrefix value

For codebook, GSI is initialising a copier struct during rebalance, for file transfer and cleanup due to any failed rebalance.
As part of the constructor for copier, a KeyPrefix is passed to the copier. This KeyPrefix is assumed to be contained in the path for any transfer and cleanup.

But as part of the cleanupFiles, the removeDir in Plama's RPC Server check if the PlasmCopyPrefix is contained the file's path. 

This causes the codebook cleanup to fail as for Codebook transfer, GSI creates another folder under the staging2 directory for codebook transfer. (/data/@2i/staging2/codebook_v1/ ).