(fix) #228: Fixes createPartitions flakiness by waiting a bit for the new partitions to appear in DescribeTopics

[aesteve]

Motivation:

Same as #233 but backporting to the 4.x branch

Conformance:

Your commits should be signed and you should have signed the Eclipse Contributor Agreement as explained in https://github.com/eclipse/vert.x/blob/master/CONTRIBUTING.md Please also make sure you adhere to the code style guidelines: https://github.com/vert-x3/wiki/wiki/Vert.x-code-style-guidelines

[aesteve]

@vietj as you requested, backporting to 4-x.

[vietj]

thanks @aesteve !