wlock: reword the devel warning
We change the wording of the developer warning:
- "lock" taken before "wlock"
+ "wlock" acquired after "lock"
The goals here are to:
- Put the "subject" as the first word,
- use "acquired" instead of "taken" since it seems more accurate.
wlock: only issue devel warning when actually acquiring the lock
Before this change, any call to 'wlock' after we acquired a 'lock' was issuing a
warning. This is wrong as the 'wlock' have been properly acquired before the
'lock' in a previous call.
We move the warning code to only issue such warnings when we are acquiring the
'wlock' -after- acquiring 'lock'. This is the expected behavior of this warning
from the start.