containers: delete redundant newline in tst_resm()

Some output strings in tst_resm() have ending newline but some have not,
and it causes disordered blank line in logfile.
Deleting all ending newline makes it uniform and good to read.

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