too many redirects

Firstly, your syntax isn't correct

http_host

[HTTP::host]

That said - you are issuing a redirect to a Host, based on the condition that the request matches the same Host header - therefore creating a loop.

If you just want to amend the URI you can use the following iRule. Alternatively, this can be achieved using a Local Traffic Profile.

when HTTP_REQUEST { 
    if {[HTTP::host] equals "electronica2018.avnet.com"} { 
        HTTP::uri "/wps/portal/e2018/" 
    } 
 }