CHIA-2282 Improve some coins checks in test_select_coins_rpc

[AmineKhaldi]

Purpose:

Improve checking min_coins, max_coins and excluded_amt_coins in test_select_coins_rpc and don't test them against None as they're lists.

Current Behavior:

We check these lists against None and then perform additional tests on them.

New Behavior:

Perform length and content tests without checking for None beforehand.

[coveralls-official]

Pull Request Test Coverage Report for Build 13029956340

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 6 of 6 (100.0%) changed or added relevant lines in 1 file are covered.
• 13 unchanged lines in 7 files lost coverage.
• Overall coverage increased (+0.04%) to 91.545%

---

Files with Coverage Reduction	New Missed Lines	%
chia/_tests/simulation/test_simulation.py	1	96.45%
chia/util/config.py	1	84.62%
chia/plotters/plotters.py	1	90.94%
chia/rpc/rpc_server.py	1	88.54%
chia/full_node/full_node.py	1	86.54%
chia/server/node_discovery.py	2	81.14%
chia/plotters/madmax.py	6	44.58%

Totals
Change from base Build 13019247618:	0.04%
Covered Lines:	105298
Relevant Lines:	114850

---

💛 - Coveralls