enable Nfs autoreconnect

[wsnipex]

Description

enables autoreconnect in libnfs.
Defaults to unlimited retries, just like standard NFS clients

configurable through AV.xml:

  <network>
    <nfsretries>10</nfsretries> <!-- 0 to disable, default: -1 (unlimited) -->
  </network>

quote from libnfs.h

* autoreconnect=<-1|0|>=1>
 *                   : Control the auto-reconnect behaviour to the NFS session.
 *                    -1 : Try to reconnect forever on session failures.
 *                         Just like normal NFS clients do.
 *                     0 : Disable auto-reconnect completely and immediately
 *                         return a failure to the application.
 *                   >=1 : Retry to connect back to the server this many
 *                         times before failing and returing an error back
 *                         to the application.

Motivation and Context

NFS should behave like smb and retry intermittent connection failures

How Has This Been Tested?

Screenshots (if appropriate):

Types of change

• Bug fix (non-breaking change which fixes an issue)
• Clean up (non-breaking change which removes non-working, unmaintained functionality)
• Improvement (non-breaking change which improves existing functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that will cause existing functionality to change)
• Cosmetic change (non-breaking change that doesn't touch code)
• None of the above (please explain below)

Checklist:

• My code follows the Code Guidelines of this project
• My change requires a change to the documentation, either Doxygen or wiki
• I have updated the documentation accordingly
• I have read the Contributing document
• I have added tests to cover my change
• All new and existing tests passed

[arnova]

Shouldn't we implement an <nfs> tag (in as.xml) that contains all the nfs options, like we did for curl?

[wsnipex]

is it worth it for just 2 options?

[wsnipex]

jenkins build this please

[arnova]

is it worth it for just 2 options?

Perhaps not yet, if it's for only 2 options atm. But let's keep it in mind for the future when more stuff gets added...

[arnova]

@wsnipex : Forgot to mention that it may be wise to disable autoreconnect when caching is enabled, like we do in smb/curl. Else the fs may hang for a longer time than desirable from a user's perspective. See https://github.com/arnova/xbmc/blob/f44fdfbf675f30c01e7639177a34544e6a6b9dad/xbmc/platform/posix/filesystem/SMBFile.cpp#L708-L712