Fix XCLAIM missing entry bug.
Fix XCLAIM missing entry bug.

This bug had a double effect:

1. Sometimes entries may not be emitted, producing broken protocol where
the array length was greater than the emitted entires, blocking the
client waiting for more data.

2. Some other time the right entry was claimed, but a wrong entry was
returned to the client.

This fix should correct both the instances.

JackieXie168/redis,JackieXie168/redis,JackieXie168/redis,JackieXie168/redis