Fix flaky tests

[qdm12]

Since some tests fail occasionally, it might be an indicator of bad logic which could cause memory leaks and/or data races. Related to #1936 and #1968

These should be investigated. The following tests were found to fail occasionally (feel free to remove/add):

• [x] #2158
• [ ] #2159
• [x] #2160
• [x] #2161
• [x] #2163
• [ ] #2162
• [x] #2164
• [x] #2165
• [x] ~#2166~ (moved to #2147)
• [x] #2167
• [x] #2168
• [x] #2280
• [ ] TestHandleTransactionMessage

[EclesioMeloJunior]

I'm investigating the TestBlockTree_GetHashByNumber

[qdm12]

Our saviour has arrived

[timwu20]

@danforbes can we change this to an epic and we will will create issues for the checkboxes in the description.