system-dpdk: Wait for MTU changes to be applied. #1975

Job	Run time
osx clang --disable-ssl	2m 49s
dpdk gcc	10s
linux deb no dpdk	5m 54s
linux gcc --disable-ssl	2m 16s
linux clang --disable-ssl	2m 17s
linux gcc c99	2m 33s
linux clang c99	2m 29s
linux gcc test	6m 20s
linux clang test asan	10m 37s
linux clang test ubsan	7m 5s
linux gcc test --enable-shared	8m 27s
linux clang test --enable-shared	8m 5s
linux gcc test dpdk	6m 41s
linux clang test dpdk	6m 35s
linux gcc test -ljemalloc	6m 33s
linux clang test -ljemalloc	6m 35s
linux gcc --enable-afxdp	2m 9s
linux clang --enable-afxdp	2m 8s
linux gcc dpdk --enable-shared	3m 5s
linux clang dpdk --enable-shared	2m 43s
linux gcc dpdk-shared	2m 21s
linux clang dpdk-shared	2m 30s
linux gcc dpdk-shared --enable-shared	2m 59s
linux clang dpdk-shared --enable-shared	2m 42s
linux gcc m32 --disable-ssl	2m 27s
	1h 48m 30s

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