Don't use Fiber locals if we're not trying to change the current thread
Don't use Fiber locals if we're not trying to change the current thread

Celluloid actually uses this by setting up locals in another
thread that it just started and thus exposed this issue.

mlarraz/rubinius,pH14/rubinius,Azizou/rubinius,sferik/rubinius,ngpestelos/rubinius,lgierth/rubinius,benlovell/rubinius,mlarraz/rubinius,Wirachmat/rubinius,Azizou/rubinius,digitalextremist/rubinius,ngpestelos/rubinius,mlarraz/rubinius,kachick/rubinius,ngpestelos/rubinius,heftig/rubinius,jsyeo/rubinius,jemc/rubinius,heftig/rubinius,dblock/rubinius,ngpestelos/rubinius,pH14/rubinius,ruipserra/rubinius,lgierth/rubinius,dblock/rubinius,lgierth/rubinius,dblock/rubinius,pH14/rubinius,benlovell/rubinius,mlarraz/rubinius,Azizou/rubinius,jemc/rubinius,jsyeo/rubinius,Wirachmat/rubinius,kachick/rubinius,benlovell/rubinius,benlovell/rubinius,heftig/rubinius,Azizou/rubinius,mlarraz/rubinius,digitalextremist/rubinius,heftig/rubinius,heftig/rubinius,pH14/rubinius,jemc/rubinius,heftig/rubinius,Wirachmat/rubinius,jemc/rubinius,sferik/rubinius,jemc/rubinius,jemc/rubinius,dblock/rubinius,sferik/rubinius,digitalextremist/rubinius,heftig/rubinius,Wirachmat/rubinius,jsyeo/rubinius,Wirachmat/rubinius,kachick/rubinius,sferik/rubinius,digitalextremist/rubinius,jsyeo/rubinius,benlovell/rubinius,Azizou/rubinius,Wirachmat/rubinius,kachick/rubinius,ngpestelos/rubinius,ngpestelos/rubinius,jsyeo/rubinius,ruipserra/rubinius,jsyeo/rubinius,lgierth/rubinius,jemc/rubinius,ruipserra/rubinius,ruipserra/rubinius,digitalextremist/rubinius,ngpestelos/rubinius,ruipserra/rubinius,kachick/rubinius,sferik/rubinius,digitalextremist/rubinius,pH14/rubinius,sferik/rubinius,Wirachmat/rubinius,mlarraz/rubinius,dblock/rubinius,sferik/rubinius,Azizou/rubinius,dblock/rubinius,pH14/rubinius,pH14/rubinius,benlovell/rubinius,ruipserra/rubinius,kachick/rubinius,digitalextremist/rubinius,lgierth/rubinius,Azizou/rubinius,lgierth/rubinius,benlovell/rubinius,kachick/rubinius,lgierth/rubinius,mlarraz/rubinius,ruipserra/rubinius,jsyeo/rubinius,dblock/rubinius,kachick/rubinius