I wouldn't worry about it.
Yes, Arginine combined with exercise has been shown in multiple studies to attenuate GH response.
The theory as to why thus far seems to be that, since both Arginine supplementation and exercise stimulate GH release significantly, when combined they cause such a strong stimulus that autonegative feedback causes a refractory period which suppresses the somatotrope. This makes the following claim from the study in question very interesting to me: "Furthermore our data shows that the GH suppression was not due to a GH or IGF-1 induced autonegative feedback loop." I need to read the full text.
Anyway, the real question is, does it matter? I would tend to agree with Rodja that these short term GH fluctuations are largely unimportant for overall muscle building. I've yet to see convincing evidence that acute hormonal response to resistance training has any significant impact on hypertrophy.
p.s. I wouldn't say that Citrulline is necessarily the answer. since it metabolizes into Arginine. However, perhaps the process of being turned into Arginine slows the GH response to pure Arginine alone? Then again, this process must happen pretty rapidly, given how quickly Citrulline's vasodilating effects occur.