Fix pagination and dataset count for Organization dataset search

[neilmb]

How to reproduce

1. Visit https://datagov-catalog-dev.app.cloud.gov/organization/americorps?dataset_search_terms=Segal

Expected behavior

The list of one matching dataset should match the parenthesized count of how many datasets match the search term and the pagination of the results table should match the size of the returned results.

Actual behavior

The count of 48 datasets is displayed and three pages of results are shown.

Sketch

The counts and pagination on the page need to be based on the query results. A test case would make two or more datasets, search for only one of them and then check that the count displayed is correct.

[FuhuXia]

Not only the count, it appears every search term ends up with 1 or 0 result.