Correct threshold naming for search and query

The connection string should be using tracing_threshold_query and tracing_threshold_search, rather than n1q}}l and {{fts. There is a small issue - CCBC-1222 which fixes how they are set, and also corrects the naming. We should have that same naming reflected in our code. Simple enough. The 2 corresponding tests in cluster_t.py should be skipped until the fix in in LCB.