fmt_pkt: make sure scapy-server is started once #2474

Job	Run time
osx clang --disable-ssl	5m 21s
dpdk gcc	5s
linux rpm fedora	7m 27s
linux gcc --disable-ssl	1m 59s
linux clang --disable-ssl	2m 0s
linux gcc test -500	13m 56s
linux gcc test 501-1000	9m 44s
linux gcc test 1001-	4m 45s
linux clang test sanitizers -300	11m 9s
linux clang test sanitizers 301-600	13m 54s
linux clang test sanitizers 601-900	8m 43s
linux clang test sanitizers 901-1200	7m 4s
linux clang test sanitizers 1201-	6m 3s
linux gcc test -ljemalloc -500	14m 40s
linux gcc test -ljemalloc 501-1000	10m 3s
linux gcc test -ljemalloc 1001-	4m 55s
linux gcc system-test-dpdk dpdk -100	10m 39s
linux gcc system-test-dpdk dpdk 101-200	15m 2s
linux gcc system-test-dpdk dpdk 201-	21m 11s
linux gcc system-test-userspace -100	9m 34s
linux gcc system-test-userspace 101-200	13m 24s
linux gcc system-test-userspace 201-	20m 2s
linux gcc system-test -100	12m 40s
linux gcc system-test 101-200	15m 48s
linux gcc system-test 201-	23m 9s
linux clang system-test sanitizers -100	14m 29s
linux clang system-test sanitizers 101-200	17m 25s
linux clang system-test sanitizers 201-	25m 2s
linux x86 gcc --disable-ssl	1m 55s
	5h 22m 8s

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