Add parameter to customize Qpid receiver capacity

In Qpid rpc backend, receiver capacity is 1 and is hardcoding.
User can not customize it. This patch adds a parameter to make
user can specify receiver capacity in conf file.

- Reference about Receiver Capacity(Prefetch) from Qpid Doc
By default, receiver requests the next message from the server
in response to each fetch call, resulting in messages being
sent to the receiver one at a time. As in the case of sending,
it is often desirable to avoid this roundtrip for each message.
This can be achieved by allowing the receiver to prefetch messages
in anticipation of fetch calls being made. The receiver needs to
be able to store these prefetched messages, the number it can hold
is controlled by the receivers capacity.

DocImpact

Change-Id: I966b512aba6bdd8e9c5cf65cae01bfd21f04f330
Closes-Bug: #1353914
Merge "Add parameter to customize Qpid receiver capacity"