MokManager: stop using StrnCat
MokManager: stop using StrnCat

StrnCat is not available in gnu-efi-3.0.5 (I did not check if it does
actually exists in 3.0.6). Moreover using strcat on a buffer where we've
just done: "buf[0] = '\0'" is a bit silly, we might as well drop the 0
termination and just use strcpy.

It seems there also is no StrnCpy in gnu-efi-3.0.5, but we are passing in
a pointer to the end of file_name minus 4, so strcpy will consume only
4 bytes anyways and there is no need for the "n".

Signed-off-by: Hans de Goede <9fa1be1a5b5729e4c6b404f34c9ce49ff4882fd8@redhat.com>

rhinstaller/shim,rhinstaller/shim,rhinstaller/shim