Changed key name to check for provider_region instead of hostname
Changed key name to check for provider_region instead of hostname

Changed key name to check for provider_region instead of hostname, EC2 specific code was changed to use provider_region column instead of hostname. Wrong key name in the check was causing validate button to not be enabled when adding EC2 provider.

https://bugzilla.redhat.com/show_bug.cgi?id=1146776
https://bugzilla.redhat.com/show_bug.cgi?id=1147075
(transferred from ManageIQ/manageiq@6403fcfa679120464731d6ea261be158e820af3b)

ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic