Enable partial matching for server commands.

Enable partial matching for server commands.

The feature was deactivated in an earlier commit which converted the
lsatt command to lopsub. The problem was that "ls" would have been
interpreted as lsatt because lsatt was the only converted command
that started with ls.

Now that all server commands are converted, the lopsub library function
lls_lookup_subcmd() does the right thing, so this patch removes the
additional test for an exact match.