vch: guard vchannel handle from uninitialized access

[sa-kib]

Zero client/server vchannel handles on error, so that no dangling pointers are left in the structure.

This is done in case vch_read()/vch_write() is accidentally called on not opened vchannel, and some non-zero non-valid leftover pointers (like h->ring) confuse validation logic.

Also validate the ring pointer when checking for opened channel.

[oleksiimoisieiev]

+1 Acked-by: Oleksii Moisieiev oleksii_moisieiev@epam.com

[sa-kib]

rebased + tags added

[oleksiimoisieiev]

@sa-kib I see chechpatch errors in this MR