Description of problem:

User should be able to pass the replica_count to the migrate call inorder to reduce the replica count of the volume. Replica_count isn't being picked up by the endpoint.

Version-Release number of selected component (if applicable):
rhsc-cb12


How reproducible:
everytime

Steps to Reproduce:
1. create a  distributed replicate volume of replicate 2
2. remove each one brick from each replicate pair while reducing the replica count
----- exmaple call--------
POST /api/clusters/0caa1ef1-aede-446d-a76e-9d0550b10fa6/glustervolumes/28a13bb7-9db3-42e7-bf67-e4245be76be3/bricks/migrate HTTP/1.1
> Content-Type: application/xml
> Accept: application/xml
> Content-Length: 462
> Host: 10.14.16.103:443
> Connection: Keebricks not from same subvol for replicap-Alive
> Usebricks not from same subvol for replicar-Agent: Apache-HttpClient/4.1.3 (java 1.5)
> Authorization: Basic YWRtaW5AaW50ZXJuYWw6cmVkaGF0
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>[\n]"
<action>[\n]"
    <bricks>[\n]"
        <replica_count>2</replica_count>[\n]"
        <brick>[\n]"
        bricks not from same subvol for replica    <name>10.14.16.131:/bricks/20131218124658163282444311</name>[\n]"
        </brick>[\n]"
        <brick>[\n]"
            <name>10.14.16.189:/bricks/20131218124658163216445332</name>[\n]"
   bricks not from same subvol for replica     </brick>[\n]"
        <brick>[\n]"
            <name>10.14.16.131:/bricks/201312181246581641358073192</name>[\n]"
        </brick>[\n]"
    </bricks>[\n]"
</action>[\n]"
bricks not from same subvol for replica
Actual results:
error message:
"bricks not from same subvol for replica"

Expected results:
error message: "volume remove-brick start: failed: Reducing replica count of volume is disallowed in glusterfs 3.4.0.49rhs"


Additional info: