Disable ssh port forwarding when value of -ssh-port is -1

[vyasgun]

This is a fix for #402

The default value for the flag is 2222 which should not happen when -1 is provided.

Tested as follows:

gvyas@Gunjans-MacBook-Pro gvisor-tap-vsock % bin/gvproxy -debug -listen unix:///tmp/network.sock -listen-qemu tcp://0.0.0.0:1234 -ssh-port 55556
INFO[0000] gvproxy version gitd1683b9b-dirty
INFO[0000] waiting for clients...
INFO[0000] listening unix:///tmp/network.sock


gvyas@Gunjans-MacBook-Pro gvisor-tap-vsock % lsof -i :55556
COMMAND   PID  USER   FD   TYPE             DEVICE SIZE/OFF NODE NAME
gvproxy 60527 gvyas    7u  IPv4 0xef6992879c346520      0t0  TCP localhost:55556 (LISTEN)

gvyas@Gunjans-MacBook-Pro gvisor-tap-vsock % bin/gvproxy -debug -listen unix:///tmp/network.sock -listen-qemu tcp://0.0.0.0:1234
INFO[0000] gvproxy version gitd1683b9b-dirty
INFO[0000] waiting for clients...
INFO[0000] listening unix:///tmp/network.sock


gvyas@Gunjans-MacBook-Pro gvisor-tap-vsock % lsof -i :2222
COMMAND   PID  USER   FD   TYPE             DEVICE SIZE/OFF NODE NAME
gvproxy 60743 gvyas    7u  IPv4 0xb6a79b454352e9f5      0t0  TCP localhost:rockwell-csp2 (LISTEN)

gvyas@Gunjans-MacBook-Pro gvisor-tap-vsock % bin/gvproxy -debug -listen unix:///tmp/network.sock -listen-qemu tcp://0.0.0.0:1234 -ssh-port -1
INFO[0000] gvproxy version gitd1683b9b-dirty
INFO[0000] waiting for clients...
INFO[0000] listening unix:///tmp/network.sock


gvyas@Gunjans-MacBook-Pro gvisor-tap-vsock % lsof -i :2222
gvyas@Gunjans-MacBook-Pro gvisor-tap-vsock %

[cfergeau]

The "DCO" failure can be fixed if you amend your commit with git commit --amend -s

[cfergeau]

Looks good to me!
A Signed-off-by needs to be added to this commit.

[vyasgun]

@cfergeau thanks, updated!

[cfergeau]

/lgtm
/approve

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cfergeau, vyasgun

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