LU-313 tests: re-enable lfsck test to run by default

LU-313 tests: re-enable lfsck test to run by default

Due to bug 13698, the lfsck part of the lfsck.sh test script was
disabled by default. After the fixes in LU-113 were landed, lfsck
should work again. Remove SKIP_LFSCK checks so lfsck.sh actually runs
lfsck instead of silently skipping it unless SKIP_LFSCK=no is set.

Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Signed-off-by: Yu Jian <yujian@whamcloud.com>
Change-Id: I430f7398b2d21db0d0755726fdcb6053f25b4b10
Reviewed-on: http://review.whamcloud.com/2497
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Wei Liu <sarah@whamcloud.com>
Reviewed-by: Johann Lombardi <johann@whamcloud.com>