CAS-14270 : Fixes to test_iterbot in tclean tests
Made a number of changes to the iterbot tests :
(a) Added gridder = 'standard' to all the tests, since that was
implicitly assumed, and is salient to the outcome of the tests.
(b) Removed the test_iterbot_*_fullsummary tests. The fullsummary
parameter is tested in multiple other places in multiple different ways.
These tests provide no additional coverage vectors and add to the
runtime of the test suite.
