github: Fix running multi-node tests on forks. #201

Job	Run time
Prepare container	3m 23s
linux rpm fedora	6m 45s
osx clang --disable-ssl	1m 52s
linux gcc --disable-ssl	2m 38s
linux clang --disable-ssl	2m 34s
linux gcc test -300	9m 13s
linux gcc test 301-600	6m 6s
linux gcc test 601- unstable	6m 32s
linux clang test sanitizers -300	12m 18s
linux clang test sanitizers 301-600	8m 40s
linux clang test sanitizers 601- unstable	10m 29s
linux gcc test -ljemalloc -300	9m 50s
linux gcc test -ljemalloc 301-600	6m 13s
linux gcc test -ljemalloc 601- unstable	6m 37s
linux gcc system-test-dpdk dpdk -100	16m 55s
linux gcc system-test-dpdk dpdk 101- unstable	12m 7s
linux gcc system-test-userspace -100	15m 46s
linux gcc system-test-userspace 101- unstable	11m 13s
linux gcc system-test -100	18m 6s
linux gcc system-test 101- unstable	14m 31s
linux clang system-test sanitizers -100	20m 30s
linux clang system-test sanitizers 101- unstable	16m 2s
linux x86 gcc --disable-ssl	2m 31s
	3h 40m 51s

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