cbbackupmgr : Benign errors/warnings in the backup.log

Build 5.0.0-3088

The backup.log has some errors and warnings which do not hamper the operation, but still should be taken care of.

[FDB INFO] Forestdb opened database file /tmp/backup/backup/2017-06-15T16_19_41.031911829+05_30/default-e2cf45e18dd118a9de076d04a177aff6/data/shard_0.fdb
[FDB ERR] Failed to open KV store 'partition830' because it doesn't exist.
[FDB ERR] Failed to open KV store 'partition955' because it doesn't exist.
[FDB ERR] Failed to open KV store 'partition981' because it doesn't exist.

The following warning appears when the backup is taken with ongoing KV operations:
2017-06-15T16:24:51.315+05:30 (DCP) (vb 863) Stream closed because all items were streamed
2017-06-15T16:24:51.827+05:30 (DCP) (vb 973) Stream closed because all items were streamed
2017-06-15T16:24:51.948+05:30 WARN: (DCP) (vb 422) Stream closed due to unhandled error `network error` backup client – couchbase.dcpClient.End() at dcp.go:367
2017-06-15T16:24:51.948+05:30 WARN: (DCP) (vb 6) Stream closed due to unhandled error `network error` backup client – couchbase.dcpClient.End() at dcp.go:367
2017-06-15T16:24:51.948+05:30 WARN: (DCP) (vb 463) Stream closed due to unhandled error `network error` backup client – couchbase.dcpClient.End() at dcp.go:367