Reduce the chance to run some rare tests

E.g., StatusBuilderPerf and TLogVersionMessagesOverheadFactor are more like
performance tests, which shouldn't be running so many times.

Without the change, a 100k-run has this many for these tests:

   1318 tests/rare/CycleWithKills.toml
   1591 tests/rare/TLogVersionMessagesOverheadFactor.toml
   1647 tests/rare/ConfigDBUnitTest.toml
   1839 tests/rare/StatusBuilderPerf.toml

After the change, a 100k-run has:

    129 tests/rare/TLogVersionMessagesOverheadFactor.toml
    151 tests/rare/CycleWithKills.toml
    160 tests/rare/StatusBuilderPerf.toml
    375 tests/rare/ConfigDBUnitTest.toml

fdbclient/BackupAgentBase.actor.cpp

@@ -847,8 +847,7 @@ ACTOR Future<int> kvMutationLogToTransactions(Database cx,
 					mutationSize = 0;
 				}
 
-				state int i;
-				for (i = 0; i < curReq.transaction.mutations.size(); i++) {
+				for (int i = 0; i < curReq.transaction.mutations.size(); i++) {
 					req.transaction.mutations.push_back_deep(req.arena, curReq.transaction.mutations[i]);
 					req.transaction.encryptedMutations.push_back_deep(req.arena,
 					                                                  curReq.transaction.encryptedMutations[i]);

tests/rare/ConfigDBUnitTest.toml

@@ -1,5 +1,5 @@
 # This test can't run as part of RandomUnitTests.toml, so run it less frequently
-testPriority = '10'
+testPriority = '50'
 
 [[test]]
 testTitle = "ConfigDBUnitTest"

tests/rare/CycleWithKills.toml

@@ -1,3 +1,7 @@
+# High priority number decreases the chance to run this test.
+# Priority 1.0 is the default in TestHarness2
+testPriority = '20'
+
 [[test]]
 testTitle = 'CycleTestWithKills'
 

tests/rare/StatusBuilderPerf.toml

@@ -1,3 +1,7 @@
+# High priority number decreases the chance to run this test.
+# Priority 1.0 is the default in TestHarness2
+testPriority = '20'
+
 [[test]]
 testTitle = 'StatusBuilderPerf'
 useDB = false

tests/rare/TLogVersionMessagesOverheadFactor.toml

@@ -1,3 +1,7 @@
+# High priority number decreases the chance to run this test.
+# Priority 1.0 is the default in TestHarness2
+testPriority = '20'
+
 [[test]]
 testTitle = 'TLogVersionMessagesOverheadFactor'
 useDB = false