fccfg.c: lock_config: Fix potential memory leak

We would malloc for every try, never cleaning up.
11 jobs for fix_lock_config_memleak in 10 minutes and 51 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Build
passed #6624342
meson android arm64 fedora

00:02:37

passed #6624340
gst-macos-10.15
meson macos

00:04:16

passed #6624337
meson-mingw-w64-build

00:06:35

manual #6624341
docker windows 1809 allowed to fail manual
meson msys2
passed #6624335
meson-shared-build

00:04:42

passed #6624336
meson-static-build

00:05:03

passed #6624338
docker windows 1809
meson vs2017 amd64

00:01:34

passed #6624339
docker windows 1809
meson vs2017 x86

00:01:34

passed #6624334
mingw-build

00:05:22

passed #6624332
shared-build

00:06:07

passed #6624333
static-build

00:05:53