setns: add ns_name in TINFO

Make it clear which namespace is enabled and being tested.

before:
setns01     0  TINFO  :  ns_fds[0]=5, ns_types[0]=0x8000000
setns01     0  TINFO  :  ns_fds[1]=6, ns_types[1]=0x20000
setns01     0  TINFO  :  ns_fds[2]=7, ns_types[2]=0x40000000
setns01     0  TINFO  :  ns_fds[3]=8, ns_types[3]=0x20000000
setns01     0  TINFO  :  ns_fds[4]=9, ns_types[4]=0x4000000

after:
setns01     0  TINFO  :  ns_name=ipc, ns_fds[0]=5, ns_types[0]=0x8000000
setns01     0  TINFO  :  ns_name=mnt, ns_fds[1]=6, ns_types[1]=0x20000
setns01     0  TINFO  :  ns_name=net, ns_fds[2]=7, ns_types[2]=0x40000000
setns01     0  TINFO  :  ns_name=pid, ns_fds[3]=8, ns_types[3]=0x20000000
setns01     0  TINFO  :  ns_name=uts, ns_fds[4]=9, ns_types[4]=0x4000000

Signed-off-by: Monson Shao <jshao@redhat.com>
Reviewed-by: Jan Stancek <jstancek@redhat.com>
Reviewed-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>