Master/slave: also send the dtb url

Change-Id: I4faf43004cbc04b524983334f1ae6b095d595e20
Add an optional `timelimit` prefix to run_command which can help with hung processes blocking the dispatcher. This is especially helpful on VExpress boards that hang when calling umount. The shell process gets killed so LAVA reboots the board, which in turn disconnects the USB, which clears the umount block. \o/ Win

Change-Id: Ic7129ac81cd3d2a1d5b4a86dfe4a00836760b2c1
Revert "Add an optional `timelimit` prefix to run_command which can help with hung processes blocking the dispatcher. This is especially helpful on VExpress boards that hang when calling umount. The shell process gets killed so LAVA reboots the board, which in tu"

This reverts commit 08453a835f0eecc89de29cfa437185e730fb417b.

Change-Id: I85cae94d4c532631b884ce44406d31da707b4ceb
selinux: rework _image_has_selinux_suport to ensure proper detection

Change-Id: Iac04aa0680ea75500c2364f237b7ccd868a85122