LU-11963 obd: Rename OS_STATE flags to OS_STATFS

LU-11963 obd: Rename OS_STATE flags to OS_STATFS

The statfs state flags are oddly named "OS_STATE_[STATE]"
Rename them to "OS_STATFS_[STATE]" to make their role clearer
and make them easier to find.

Test-Parameters: trivial
Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: I3f43b3e73155d9fbd8b3e0fa52e7f4d26b9d2f89
Reviewed-on: https://review.whamcloud.com/34289
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Patrick Farrell <farr0186@gmail.com>