rstp: Fix deadlock with patch ports. #2079

Job	Run time
osx clang --disable-ssl	4m 45s
linux gcc --disable-ssl	2m 29s
linux clang --disable-ssl	2m 40s
linux gcc c99	2m 3s
linux clang c99	2m 2s
linux gcc test 4.14	7m 41s
linux clang test 4.14 asan	12m 36s
linux gcc test --enable-shared	9m 35s
linux clang test --enable-shared	9m 34s
linux gcc test dpdk	7m 35s
linux clang test dpdk	7m 56s
linux gcc test -ljemalloc	7m 22s
linux clang test -ljemalloc	7m 35s
linux gcc 5.8 5.5 5.4 4.19	5m 32s
linux clang 5.8 5.5 5.4 4.19	5m 44s
linux gcc 4.14 4.9 4.4	3m 50s
linux clang 4.14 4.9 4.4	3m 56s
linux gcc afxdp 5.4	3m 12s
linux clang afxdp 5.4	3m 0s
linux gcc dpdk --enable-shared	3m 2s
linux clang dpdk --enable-shared	2m 55s
linux gcc dpdk-shared	2m 24s
linux clang dpdk-shared	2m 25s
linux gcc dpdk-shared --enable-shared	3m 11s
linux clang dpdk-shared --enable-shared	2m 52s
linux gcc m32 --disable-ssl	2m 3s
linux gcc deb	8m 34s
	2h 16m 33s

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