wrapper: null terminated string in cgroup_add_controller()

wrapper: null terminated string in cgroup_add_controller()

Fix non-terminated string warning, reported by Coverity tool:

CID 258271 (#1 of 1): String not null terminated (STRING_NULL).
string_null: Passing unterminated string cgc->name to strcmp, which
expects a null-terminated string.

This issue was reported following the path src/abstraction-common.c:
- cgroup_convert_cgroup()
  - cgroup_add_controller()

Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>