tests/int/dev: only call lsblk once
tests/int/dev: only call lsblk once

The "runc run [device cgroup allow rm block device]" test calls lsblk
three times to get device name, minor and major number. This creates a
potential problem when the devices are changed between the calls.

Simplify the code by using bash read together with IFS (as there's no
way to have lsblk output MAJOR:MINOR pair without a semicolon).

Note that head -n 1 is not needed as read already reads a single line.

[v2: don't use PATH as CentOS7's lsblk does not support it.]

Signed-off-by: Kir Kolyshkin <3a017b8ddb3f9cf3e4a59978b004111bdeb97f08@gmail.com>

opencontainers/runc,dqminh/runc,opencontainers/runc,kolyshkin/runc,dqminh/runc,rhatdan/runc,kolyshkin/runc,dqminh/runc,rhatdan/runc,kolyshkin/runc,opencontainers/runc,rhatdan/runc,rhatdan/runc,dqminh/runc,opencontainers/runc,kolyshkin/runc