core: Fixing regression in PrivilegeHelper that prevented running as non-root

PrivilegeHelper was properly initialized only when general section was
present.  When section was omitted, s_privilegedUid/s_privilegedGid/s_normalUid/s_normalGid
variables was not properly initialized (set to 0), resulting in
exception during the subsequent PrivilegeHelper::drop call.

Change-Id: Iffd7f05e7e6c86d227da2c9b7920ca6e3b607211