iptb init fails with an unhelpful error if init fails

[Stebalien]

If iptb init fails (e.g., because a bad flag was passed), iptb throws away any error messages from ipfs and, instead, complains that the node wasn't initialized.

To reproduce:

iptb testbed create --count 1 --type localipfs
iptb init -- -p foobar

This fails with:

ipfs not initialized, please run 'ipfs init'
node[0]
gx/ipfs/QmckeQ2zrYLAXoSHYTGn5BDdb22BqbUoHEHm8KZ9YWRxd1/iptb/commands.mapWithOutput.func1
	/home/steb/projects/go/src/gx/ipfs/QmckeQ2zrYLAXoSHYTGn5BDdb22BqbUoHEHm8KZ9YWRxd1/iptb/commands/utils.go:195
runtime.goexit
	/usr/lib/go/src/runtime/asm_amd64.s:1333

I'd expect it to tell me:

initializing IPFS node at /tmp/test
generating 2048-bit RSA keypair...done
peer identity: QmeTHw4JpNPSEbEd1afyW1MAce2tqp65znksFsn4TwAs71
Error: invalid configuration profile: foobar