PHOENIX-7828 De-flake UCFWithDisabledIndexIT

[apurtell]

UCFWithDisabledIndexIT was flaky due to two independent races.

First, the tests swap MetaDataEndpointImpl on SYSTEM.CATALOG with a TestMetaDataEndpointImpl that throws DoNotRetryIOException("Not allowed") on every getTable RPC, but TestUtil.addCoprocessor() only polls until the master TableDescriptor is updated and does not wait for region servers to reopen SYSTEM.CATALOG with the new coprocessor. This creates five race sites where client work runs before the swap is visible.

Second, testUcfWithNoGetTableCalls created its data table with UPDATE_CACHE_FREQUENCY=20000, then performed 7 DDLs and 7 UPSERTs before a final SELECT that is expected to be served entirely from the client metadata cache. Whenever wall-clock delay between CREATE TABLE and the SELECT exceeded 20 s the cache expired, a getTable RPC was issued, and the stub rejected it.

Add a waitForCoprocessorOnSystemCatalog(Class) helper that polls region.getCoprocessorHost().findCoprocessor(className) on every SYSTEM.CATALOG region (up to 10 s) and call it after each of the five swaps.

Change testUcfWithNoGetTableCalls's CREATE TABLE from UPDATE_CACHE_FREQUENCY=20000 to UPDATE_CACHE_FREQUENCY=NEVER, which decouples the assertion from wall-clock time.