wrapper.c: fix string non-termination warning

wrapper.c: fix string non-termination warning

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

CID 258266 (#1 of 1): String not null-terminated (STRING_NULL).
string_null: Passing unterminated string con to strtok, which expects a
null-terminated string.

Fix the warning in create_cgroup_from_name_value_pairs(), by adding
'\0'.

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