Description of problem:
-----------------------
'gluster volume set' has inherent property of suggesting the user proper 'key' close to the one that user typed incrrectly. This could be thought of as a suggestion which helps user to correct the 'key', if he meant it wrongly.

These keys are of format, 'domain.key' combination.
For example, 'performance.read-ahead'
This format allows same key in different domain.
When such thing happens, auto-suggestion from gluster cli doesn't help the user, rather confused him

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

How reproducible:
-----------------
always

Steps to Reproduce:
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1.execute 'gluster volume set <vol-name> outstanding-rpc-limit 32'

Actual results:
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'outstanding-rpc-limit' was available two different domains, 'nfs' and 'server'.
And there is a meaningless auto-suggestion, suggesting the same key again, rather than explaining user that there are 2 domains containing the same key

Expected results:
-----------------
There could be a better and meaningful suggestion

Additional info:
----------------
[Fri Jul 18 11:28:26 UTC 2014 root.37.136:~ ] # gluster volume set dv outstanding-rpc-limit 3
volume set: failed: option : outstanding-rpc-limit does not exist
Did you mean outstanding-rpc-limit?

[Fri Jul 18 11:28:33 UTC 2014 root.37.136:~ ] # gluster volume set dv server.outstanding-rpc-limit 3
volume set: success

[Fri Jul 18 11:28:47 UTC 2014 root.37.136:~ ] # gluster volume set dv nfs.outstanding-rpc-limit 3
volume set: success

[Fri Jul 18 11:28:53 UTC 2014 root.37.136:~ ] # gluster v i

Volume Name: dv
Type: Distribute
Volume ID: 6b811482-bc48-4142-b988-2b8efe7cae46
Status: Started
Snap Volume: no
Number of Bricks: 1
Transport-type: tcp
Bricks:
Brick1: 10.70.37.136:/rhs/brick1/b1
Options Reconfigured:
nfs.outstanding-rpc-limit: 3
server.outstanding-rpc-limit: 3
performance.readdir-ahead: on
auto-delete: disable
snap-max-soft-limit: 90
snap-max-hard-limit: 256

[Fri Jul 18 11:28:58 UTC 2014 root.37.136:~ ] # gluster volume set dv outstanding-rpc-limit 3
volume set: failed: option : outstanding-rpc-limit does not exist
Did you mean outstanding-rpc-limit?