Add sleep to search_for function, so that node can be searched

Because Chef server build node index need some time, so when a node is
bootstrapped, it takes some time before it is searchable. So I added a
timeout for Chef building node index.

Closes-bug: 1208201
Change-Id: I55eb383ce98e4765c412ece799f7885e690ab188
Merge "Add sleep to search_for function, so that node can be searched"