tools: print daemon start cmd, vtysh_b cmd

tools: print daemon start cmd, vtysh_b cmd

When starting a daemon, print the full command run by the init script to
start it. This gives more information and is especially helpful when
debugging wrap commands.

Also add some more logs to vtysh_b to print the command used there,
log when we exit early because frr.conf doesn't exist, and simplify the
code path for creating the command to use.

Signed-off-by: Quentin Young <qlyoung@nvidia.com>