Rename get_hypervisor_hostanme() to get_hypervisor_hostname()

- get_hypervisor_hostname() is called in vCenter related test suite
  fuelweb_test/tests/test_vcenter.py

Closes-bug: #1406525
Change-Id: I3c4f36fbd45c98e8eec5e1db3c7256643e732ddc
Merge "Rename get_hypervisor_hostanme() to get_hypervisor_hostname()"