getRolePermissions of UserAdmin service does not check for role existency

[nipunthathsara]

Description:
Calling getRolePermissions for non-existing role returns with all permissions with false value. Should validate the role existency within the same call and return an appropriate response.

Affected Product Version:
IS-5.3.0

Steps to reproduce:

1. Call getRolePermissions of userAdmin service with non-existing role name
   Eg: -
   <soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://org.apache.axis2/xsd"> <soapenv:Header/> <soapenv:Body> <xsd:getRolePermissions> <!--Optional:--> <xsd:roleName>mockrole</xsd:roleName> </xsd:getRolePermissions> </soapenv:Body> </soapenv:Envelope>