sys: retry lsetpag if errno is EINTR

sys: retry lsetpag if errno is EINTR

The variable errno might be set by some system calls to indicate the
reason why the system call in question did not work as expected. If the
setpag system call is interrupted by a signal, the value of errno will
be EINTR. This value means that setpag did not succeed because it was
interrupted.

If lsetpag did not succeed and errno is equal to EINTR, try again.

Reviewed-on: https://gerrit.openafs.org/12295
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Cheyenne Wills <cwills@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
(cherry picked from commit 2ae2a15c9dc9b26eaa15964cc96fdeeb6d82c74c)

Change-Id: I58d4aa633e5cadea2bc7b222f68306f07657b754
Reviewed-on: https://gerrit.openafs.org/13975
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Cheyenne Wills <cwills@sinenomine.net>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>