ext4: Return after ext4_error in case of failures

This fix some instances where we were continuing after calling
ext4_error. ext4_error call panic only if errors=panic mount option is
set. So we need to make sure we return correctly after ext4_error call

Reported by: Adrian Bunk <bunk@kernel.org>

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>