cpp: do not mention -1 for command_port option
cpp: do not mention -1 for command_port option

-1 is not a valid port number and thus do not mean "no gRPC command server".

If you try to pass -1 to command_port you get:

$ bazel --command_port=-1 build //...
Invalid argument to --command_port: '-1'.
Must be a valid port number or 0.

Change-Id: I6c17167f6a285b21fcd064cea8bdc7e6770ac984
PiperOrigin-RevId: 155352835

ulfjack/bazel,ButterflyNetwork/bazel,werkt/bazel,akira-baruah/bazel,dslomov/bazel-windows,ulfjack/bazel,akira-baruah/bazel,twitter-forks/bazel,werkt/bazel,dropbox/bazel,davidzchen/bazel,davidzchen/bazel,dslomov/bazel,aehlig/bazel,twitter-forks/bazel,dslomov/bazel-windows,variac/bazel,spxtr/bazel,dslomov/bazel,juhalindfors/bazel-patches,werkt/bazel,variac/bazel,damienmg/bazel,spxtr/bazel,katre/bazel,juhalindfors/bazel-patches,ulfjack/bazel,safarmer/bazel,dslomov/bazel-windows,dslomov/bazel-windows,damienmg/bazel,bazelbuild/bazel,snnn/bazel,akira-baruah/bazel,davidzchen/bazel,dslomov/bazel-windows,aehlig/bazel,variac/bazel,spxtr/bazel,damienmg/bazel,ButterflyNetwork/bazel,cushon/bazel,dslomov/bazel,bazelbuild/bazel,variac/bazel,variac/bazel,dropbox/bazel,katre/bazel,perezd/bazel,bazelbuild/bazel,perezd/bazel,meteorcloudy/bazel,spxtr/bazel,safarmer/bazel,perezd/bazel,safarmer/bazel,ulfjack/bazel,akira-baruah/bazel,cushon/bazel,meteorcloudy/bazel,aehlig/bazel,perezd/bazel,juhalindfors/bazel-patches,davidzchen/bazel,akira-baruah/bazel,katre/bazel,damienmg/bazel,bazelbuild/bazel,davidzchen/bazel,safarmer/bazel,meteorcloudy/bazel,perezd/bazel,meteorcloudy/bazel,snnn/bazel,snnn/bazel,variac/bazel,cushon/bazel,ButterflyNetwork/bazel,ButterflyNetwork/bazel,snnn/bazel,variac/bazel,snnn/bazel,ulfjack/bazel,juhalindfors/bazel-patches,dslomov/bazel,aehlig/bazel,dropbox/bazel,ButterflyNetwork/bazel,twitter-forks/bazel,meteorcloudy/bazel,juhalindfors/bazel-patches,meteorcloudy/bazel,bazelbuild/bazel,aehlig/bazel,dslomov/bazel,akira-baruah/bazel,bazelbuild/bazel,werkt/bazel,snnn/bazel,twitter-forks/bazel,spxtr/bazel,twitter-forks/bazel,snnn/bazel,twitter-forks/bazel,dropbox/bazel,katre/bazel,safarmer/bazel,damienmg/bazel,davidzchen/bazel,damienmg/bazel,cushon/bazel,dropbox/bazel,juhalindfors/bazel-patches,aehlig/bazel,spxtr/bazel,twitter-forks/bazel,dslomov/bazel,perezd/bazel,damienmg/bazel,davidzchen/bazel,dslomov/bazel,perezd/bazel,meteorcloudy/bazel,ulfjack/bazel,katre/bazel,ulfjack/bazel,cushon/bazel,dslomov/bazel-windows,werkt/bazel,werkt/bazel,juhalindfors/bazel-patches,ButterflyNetwork/bazel,aehlig/bazel,spxtr/bazel,safarmer/bazel,dropbox/bazel,cushon/bazel,katre/bazel