xrootd endpoint: Increase the read() request timeout from 30 to 90 seconds

If a server fails to respond, the client waits until the stream timeout expires before retrying. The stream timeout uses the default of 60 seconds.

By increasing the request timeout to 90 seconds, it allows time for a retry. This will hopefully avoid spurious warnings.

Timeout diagram: https://xrootd.slac.stanford.edu/doc/xrdcl-docs/www/xrdcldocs.html#x1-580004.3.6