travis: remove debug prints

    % mount
    /vz/private/1546939 on / type simfs (rw)
    proc on /proc type proc (rw,noexec,nosuid,nodev)
    sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
    none on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
    none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev)
    none on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755)
    /dev/null on /var/ramfs type tmpfs (rw,noatime,size=256m)
    none on /run/lock type tmpfs (rw,noexec,nosuid,nodev,size=5242880)
    none on /run/shm type tmpfs (rw,nosuid,nodev)
    % ls -lah /dev/shm/
    total 16K
    drwxr-xr-x 2 root root 4.0K Jan  9 08:26 .
    drwxr-xr-x 5 root root  12K Mar 23 12:27 ..
    % -ls -lah /run/shm/
    total 0
    drwxrwxrwt  2 root root  40 Mar 23 12:27 .
    drwxr-xr-x 14 root root 500 Mar 23 12:27 ..