This patch fixes four potential hangs:

1. A deadlock can occur between a migration and 
a flush on a file. One thread will be waiting in 
insert_actRange_onto_list() and the other in 
cfs_condio_cc_excl_mode_enter().

2. A deadlock can occur when a clone fileset is mounted,
and there are racing threads that are modifying a common 
file via memory mapping.  One thread will be waiting in
cow_get_locks and the other in msfs_mmap.

3. A deadlock can occur when a clone fileset is mounted,
and a file is being extended using DirectIO.  The thread
will hang in insert_actRange_onto_list.

4. A deadlock can occur when a clone fileset is mounted,
and a file is being truncated using DirectIO.  The thread
will hang in insert_actRange_onto_list.

Problem 1
---------
0 thread_block
1 sleep_prim
2 mpsleep
3 insert_actRange_onto_list
4 msfs_flush_and_invalidate
5 cfs_comm_open
6 cfscall_open
7 cfs_open
8 vn_open
9 copen
10 syscall
11 _Xsyscall

AND

0 thread_block
1 lock_write
2 cfs_condio_cc_excl_mode_enter
3 migrate_get_clu_locks
4 migrate_normal
5 mig_migrate
6 bs_migrate
7 ss_vd_migrate
8 ss_move_file
9 ss_work_thd_pool

Problem 2
---------
0 thread_block
1 lock_read
2 cow_get_locks
3 bs_cow_pg
4 bs_cow
5 bs_pinpg_clone
6 bs_pinpg_get
7 msfs_getpage
8 u_vp_fault
9 u_map_fault
10 vm_fault
11 trap
12 _XentMM

AND 

0 thread_block
1 lock_write
2 msfs_mmap
3 smmap
4 syscall
5 _Xsyscall

Problem 3
---------
0 thread_block         
1 sleep_prim           
2 mpsleep              
3 insert_actRange_onto_list
4 cow_get_locks
5 bs_cow_pg
6 bs_cow
7 bs_pinpg_clone
8 bs_pinpg_ftx
9 copy_and_del_frag
10 fs_write_add_stg
11 fs_write
12 msfs_write
13 vn_pwrite
14 prwuio
15 pwrite
16 syscall
17 _Xsyscall

Problem 4
---------
0 thread_block
1 sleep_prim
2 mpsleep
3 insert_actRange_onto_list
4 fs_setattr
5 msfs_setattr
6 cfs_comm_setattr
7 cfscall_setattr
8 cfs_setattr
9 vn_open
10 copen
11 syscall
12 _Xsyscall

