ovsdb-server: Fix excessive memory usage on DB open. #2191

Job	Run time
dpdk gcc	8s
osx clang --disable-ssl	4m 13s
linux rpm fedora	6m 8s
linux deb no dpdk	8m 41s
linux gcc --disable-ssl	3m 52s
linux clang --disable-ssl	4m 4s
linux gcc test	10m 51s
linux clang test asan	23m 23s
linux clang test ubsan	14m 39s
linux gcc test --enable-shared	18m 19s
linux clang test --enable-shared	19m 31s
linux gcc test dpdk	10m 45s
linux clang test dpdk	10m 22s
linux gcc test -ljemalloc	13m 19s
linux clang test -ljemalloc	12m 25s
linux gcc --enable-afxdp	3m 18s
linux clang --enable-afxdp	3m 0s
linux gcc dpdk --enable-shared	6m 10s
linux clang dpdk --enable-shared	5m 31s
linux gcc dpdk-shared	3m 51s
linux clang dpdk-shared	4m 9s
linux gcc dpdk-shared --enable-shared	6m 37s
linux clang dpdk-shared --enable-shared	5m 0s
linux gcc m32 --disable-ssl	3m 19s
	3h 21m 35s

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