Incorrect work rally info find for SLA

If you type 'rally info find <query>' rally will suggest us docs that
 will be match by query. Even if you have one typo. otherwise it sugest
 you list of docs that you are possibly looking for. But if you type
'rally info find failure_rate' there output would be: "Failed to find
any docs for query: 'failure_rate'". Instead there must be information
about SLA(failure_rate): "Failure rate minimum and maximum in percents.".

Change-Id: Ie6c59e4091cddd8f5e81e2123cad1367b397a9b6
Closes-bug: 1399675