mqns tests: runmqnsstest.sh -> runtest/containers

Extracted mqns tests from runmqnstest.sh and container_test.sh and added them
one by one to runtest/containers.

Signed-off-by: Artem Savkov <asavkov@redhat.com>
netns tests: runnetnstest.sh -> runtest/containers

Extracted netns tests from runnetnstest.sh and container_test.sh and added them
one by one to runtest/containers.
vsftpd start/stop is moved to par_child_ftp.sh
iproute2 check is moved to check_iproute() function in netn_helper.h

Signed-off-by: Artem Savkov <asavkov@redhat.com>
ipcns tests: runipcnstest.sh -> runtest/containers

Extracted sysvipc tests from runipcnstest.sh and container_test.sh and added
them one by one to runtest/containers.

Signed-off-by: Artem Savkov <asavkov@redhat.com>
uts tests: runutstest.sh -> runtest/containers

Extracted utsname tests from runutstest.sh and container_test.sh and added
them one by one to runtest/containers.
hostname recovery moved to utstest.c. tst_exits removed from P2 so that
hostname is actually recovered.
README is removed as it was mostly duplicating utstest.c's header.

Signed-off-by: Artem Savkov <asavkov@redhat.com>
check_for_unshare test removed from containers tests

Removed this test as it doesn't seem to be needed any more, it just checks
availability of unshare(2) call and all the code that actually uses it has it
wrapped with appropriate #if HAVE_UNSARE clauses.

Signed-off-by: Artem Savkov <asavkov@redhat.com>
kernel/containers/netns cleanup

Updated netns testcases to use tst_resm/tst_exit interfaces instead of plain
exits and call subexecutables using just their name instead of full path as
it is guaranteed that they are within $PATH.

Signed-off-by: Artem Savkov <asavkov@redhat.com>