Fix identified coverity scan defects

[wkozaczuk]

I have recently run a couple of the Coverity scan reports for OSv which can be found here - please click on "View Defects" on the right.

I have also set it up to classify the defects into a number of buckets:

• zfs (at this moment all of ZFS code is outside of kernel)
• vfs
• musl
• other

Obviously, the last three are all part of the kernel.

I suspect some of the reported defects are false positives (see the "Uninitialized pointer read" in fs/vfs/vfs_lookup.cc,vfs_mount.cc, and vfs_syscalls.cc) but some are probably worth fixing. There is a total of 106 high-impact issues in kernel and 54 in the zfs subtree.