[BUGFIX] Avoid SQL error in indexed_search indexer on PostgreSQL

This patch fixes the SQL query inserting index_rel records on PostgreSQL
by making sure an integer instead of a float is inserted in the freq
column (which is defined as smallint).

Resolves: #91660
Releases: master, 10.4, 9.5
Change-Id: Id994bce0ca89105f03446c5fe13516774b0a16a0