tests: Fix flaky "ovn-controller: Multiple OVS interfaces ...". #2568

Job	Run time
Prepare container	3m 16s
linux rpm fedora	6m 46s
osx clang --disable-ssl	2m 6s
linux gcc --disable-ssl	2m 36s
linux clang --disable-ssl	2m 49s
linux gcc test -300	10m 1s
linux gcc test 301-600	6m 59s
linux gcc test 601- unstable	7m 22s
linux clang test sanitizers -300	13m 25s
linux clang test sanitizers 301-600	9m 38s
linux clang test sanitizers 601- unstable	12m 22s
linux gcc test -ljemalloc -300	10m 36s
linux gcc test -ljemalloc 301-600	7m 6s
linux gcc test -ljemalloc 601- unstable	7m 29s
linux gcc system-test-dpdk dpdk -100	16m 57s
linux gcc system-test-dpdk dpdk 101- unstable	16m 13s
linux gcc system-test-userspace -100	15m 58s
linux gcc system-test-userspace 101- unstable	14m 53s
linux gcc system-test -100	18m 25s
linux gcc system-test 101- unstable	19m 5s
linux clang system-test sanitizers -100	20m 15s
linux clang system-test sanitizers 101- unstable	20m 59s
linux x86 gcc --disable-ssl	2m 32s
	4h 7m 48s

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