tools/cgexec: fix memory leak in find_scope_pid()

tools/cgexec: fix memory leak in find_scope_pid()

Fix a memory leak, reported by the Coverity tool.

CID 321265 (#1-2 of 2): Resource leak (RESOURCE_LEAK)37. leaked_storage:
Variable pids going out of scope leaks the storage it points to.

find_scope_pid (), calls cgroup_get_procs() to get the pids of the
tasks under cgroup name, and it's up to the caller to free the allocated
pids. Fix it by calling free(pids) after every call to
cgroup_get_procs().

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