Medium: crm_resource: fix a memleak

$ ./BasicSanity.sh -v cli

[..]

• Passed: cibadmin - Create a resource =#=#=#= Begin test: Create a resource meta attribute =#=#=#= Set 'dummy' option: id=dummy-meta_attributes-is-managed set=dummy-meta_attributes name=is-managed=false

+==00:00:00:01.966 1247== 11 bytes in 1 blocks are definitely lost in loss record 2 of 10
+==00:00:00:01.966 1247== at 0x4A08987: calloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
+==00:00:00:01.966 1247== by 0x403AA4: main (crm_resource.c:522)
+==00:00:00:01.966 1247==
[..]

Signed-off-by: Jan Pokorný <jpokorny@redhat.com>