ext4: fix error handling in ext4_fc_record_modified_inode()

In the Linux kernel, the following vulnerability has been resolved: ext4: fix error handling in ext4_fc_record_modified_inode() Current code does not fully takes care of krealloc() error case, which could lead to silent memory corruption or a kernel bug. This patch fixes that. Also it cleans up some duplicated error handling logic from various functions in fast_commit.c file.