db-ctl-base: Fix memory leak of db commands. #2332

Job	Run time
osx clang --disable-ssl	4m 11s
linux gcc --disable-ssl	3m 12s
linux clang --disable-ssl	3m 4s
linux gcc c99	4m 1s
linux clang c99	3m 2s
linux gcc test 3.16	13m 19s
linux clang test 3.16 asan	20m 29s
linux gcc test --enable-shared	18m 9s
linux clang test --enable-shared	14m 25s
linux gcc test dpdk	12m 49s
linux clang test dpdk	10m 16s
linux gcc test -ljemalloc	13m 7s
linux clang test -ljemalloc	10m 20s
linux gcc 5.8 5.5 5.4 4.19	9m 16s
linux clang 5.8 5.5 5.4 4.19	7m 36s
linux gcc 4.14 4.9 4.4 3.16	7m 54s
linux clang 4.14 4.9 4.4 3.16	8m 50s
linux gcc afxdp 5.3	5m 45s
linux clang afxdp 5.3	3m 57s
linux gcc dpdk --enable-shared	5m 18s
linux clang dpdk --enable-shared	4m 34s
linux gcc dpdk-shared	4m 23s
linux clang dpdk-shared	3m 16s
linux gcc dpdk-shared --enable-shared	4m 38s
linux clang dpdk-shared --enable-shared	3m 58s
linux gcc m32 --disable-ssl	3m 52s
linux gcc deb	9m 29s
	3h 33m 10s

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