retry requests in e2e tests #1756

Job	Run time
checkstyle	23s
e2e_tests (latest, 7.2)	16m 53s
unit_tests (latest, 7.2, singlesite)	14m 1s
e2e_tests (latest, 8.1)	17m 11s
unit_tests (latest, 7.2, multisite)	12m 54s
e2e_tests (trunk, 7.2)	16m 33s
unit_tests (latest, 8.1, singlesite)	15m 20s
e2e_tests (trunk, 8.1)	18m 6s
unit_tests (latest, 8.1, multisite)	13m 39s
unit_tests (5.2, 7.2, singlesite)	12m 37s
unit_tests (5.2, 7.2, multisite)	14m 15s
	2h 31m 52s

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