sbin/hammer: Make hammer commands print root volume path

sbin/hammer: Make hammer commands print root volume path

Base on the change made by the previous commit, this commit adds
the root volume path information (not root volume#) to hammer info
and hammer volume-list commands. hammer volume-list shows the path
only on -v. This enables users to explicitly know the root volume.

 [A] The existing /sbin/hammer
 # hammer -v volume-list /HAMMER
 /dev/da1
 /dev/da2
 /dev/da3
 # hammer info /HAMMER | grep Root
         Root Volume         0

 [B] With this commit
 # ./hammer -v volume-list /HAMMER
 0       /dev/da1 (Root Volume)
 1       /dev/da2
 2       /dev/da3
 # hammer info /HAMMER | grep Root
         Root Volume         /dev/da1