localrepo: clear _filecache on rollback (issue3261)
Files are being replaced by rollback but the corresponding data in localrepo
isn't actually updated for things like bookmarks, phases, etc. Then when
rollback is done, the cache is updated thinking it has the most up-to-date
data, where in fact it is still pre-rollback.
We clear _filecache to force everything to be recreated.
os = <unloaded module 'os'>
os.system = <built-in function system>
os = <module 'os' from '?'>
util = <unloaded module 'util'>
util.system = <function system at 0x?>
util = <module 'mercurial.util' from '?'>
util.system = <function system at 0x?>
fred = <unloaded module 're'>
re = <unloaded module 'sys'>
fred = <unloaded module 're'>
fred.sub = <function sub at 0x?>
fred = <proxied module 're'>
re = <unloaded module 'sys'>
re.stderr = <open file '<whatever>', mode 'w' at 0x?>
re = <proxied module 'sys'>