lib/qa.py: raise ValueError if file isn't an ELF

Instead of raising a generic Exception that can't be handled specifically, raise
a ValueError.  Also update the callers so any unexpected exceptions are not
ignored.

Also, rename isBigEngian() to isBigEndian().

(From OE-Core rev: c136652f9c0b35aafa393e63567daf029ae03929)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/insane.bbclass

@@ -792,7 +792,9 @@ def package_qa_walk(warnfuncs, errorfuncs, skip, package, d):
             elf = oe.qa.ELFFile(path)
             try:
                 elf.open()
-            except:
+            except (IOError, ValueError):
+                # IOError can happen if the packaging control files disappear,
+                # ValueError means the file isn't an ELF.
                 elf = None
             for func in warnfuncs:
                 func(path, package, d, elf, warnings)