db-ctl-base: Fix memory leak of db commands. #1898

Job	Run time
dpdk gcc	8s
linux rpm fedora	9m 1s
linux deb no dpdk	9m 24s
osx clang --disable-ssl	3m 23s
linux gcc --disable-ssl	3m 5s
linux clang --disable-ssl	2m 58s
linux gcc c99	3m 18s
linux clang c99	4m 13s
linux gcc test	10m 23s
linux clang test asan	20m 24s
linux clang test ubsan	11m 32s
linux gcc test --enable-shared	15m 9s
linux clang test --enable-shared	14m 16s
linux gcc test dpdk	11m 7s
linux clang test dpdk	11m 11s
linux gcc test -ljemalloc	11m 30s
linux clang test -ljemalloc	11m 33s
linux gcc --enable-afxdp	3m 26s
linux clang --enable-afxdp	3m 41s
linux gcc dpdk --enable-shared	4m 34s
linux clang dpdk --enable-shared	5m 4s
linux gcc dpdk-shared	3m 49s
linux clang dpdk-shared	3m 33s
linux gcc dpdk-shared --enable-shared	4m 31s
linux clang dpdk-shared --enable-shared	5m 25s
linux gcc m32 --disable-ssl	3m 17s
	3h 9m 55s

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