Fix config gen -x flag

[0pcom]

Did you run make format && make check?
yes
Changes:

• fix retain remote hypervisor configuration; skywie-cli config gen -x flag

How to test this PR:

git clone https://github.com/the-skycoin-project/skywire
cd skywire
git checkout fix-xflag
go run cmd/skywire-cli/skywire-cli.go config gen -r --hvpks 022769f159bb6f67c13140a214d5da0f2192d0881f00449460c458e17eb60115a7
 go run cmd/skywire-cli/skywire-cli.go config gen -rx

the config is successfully regenerated and the remote hypervisor configuration is retained

compare to the current behavior of the rc2 release candidate binaries