Agony, Hydrophobia and viruses in the light of evolutionary principles
The hydrophobia symptom is most likely a bi-product of the effects the virus has on the brain and not an evolutionarily derived strategy to create an appropriate environment to reproduce in. Just the same as other symptoms the infection causes, like fever for example, is a reaction the body has to the presence of the virus and not something the virus is doing on purpose to set up a better environment. 

A bit old, but check out [1]: "Hydrophobia may represent an exaggerated respiratory tract irritant reflex with associated arousal potentiated by the selective destruction of brain stem inhibitory systmes."

So basically the virus is indirectly causing a fear of water. The destruction of brain cells and inflammation caused by the presence of the virus in the central nervous system cause a reflex in the respiratory tract which manifests as muscle spasms and renders the patient, who is already pretty out of it at this stage, unable and very unwilling to drink any fluids [2].

[1] http://europepmc.org/abstract/MED/982512 (Warrell DA, Transactions of the Royal Society of Tropical Medicine and Hygiene [1976, 70(3):188-195])

[2] http://publichealth.lacounty.gov/vet/rabiesmanual/clinical.htm