BUG 801764 - xfs_check and xfs_repair should fail if device mounted

[pv@xxxxxxxxxxxxx (dxm@xxxxxxxxxxxx)]

View Incident: 
http://co-op.engr.sgi.com/BugWorks/code/bwxquery.cgi?search=Search&wlong=1&view_type=Bug&wi=801764

Submitter : dxm                       Submitter Domain : engr               
Assigned Engineer : dxm               Assigned Domain : engr                
Assigned Group : xfs-linux            Category : software                   
Customer Reported : F                 Priority : 4                          
Project : xfs-linux                   Status : open                         
Description :
both "xfs_check" and "xfs_repair -n" may be run on a mounted
filesystem and will usually produce lots of warnings about
filesystem corruption due to the inconsistent state the FS
is in.

Both tools should fail or at least warn that the FS is mounted
before proceeding. 

xfs_logprint should also warn when run on a mounted FS, but
can still be useful when mounted.