To avoid actions that require cap_net_admin permissions on build
servers, add this option to "dry run" all kernel GTP actions. Same will
be added for netfilter rules.
On startup, osmo-upf opens sockets to GTP kernel module / NFT ctx.
However, on build servers, this would require giving cap_net_admin
permissions just to run the VTY tests.
Related: SYS#5599
Change-Id: I3b9c796186307fd8562abcff3f0ccfab0e88b6c8