pmdalio: wrap refresh routine with exception handling
pmdalio: wrap refresh routine with exception handling

When no iSCSI devices have been created yet the kernel
modules are not necessarily loaded.  This'll result in
exceptions from rtslib - so mask these (logged once).

Resolves Red Hat BZ #1843792.

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp