iotests: Drop use of bash keyword 'function'

Bash allows functions to be declared with or without the leading
keyword 'function'; but including the keyword does not comply with
POSIX syntax, and is confusing to ksh users where the use of the
keyword changes the scoping rules for functions.  Stick to the
POSIX form through iotests.

Done mechanically with:
  sed -i 's/^function //' $(git ls-files tests/qemu-iotests)

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20181116215002.2124581-1-eblake@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
diff --git a/tests/qemu-iotests/177 b/tests/qemu-iotests/177
index 7bf8e1d..f0c1155 100755
--- a/tests/qemu-iotests/177
+++ b/tests/qemu-iotests/177
@@ -85,7 +85,7 @@
 echo
 echo "== verify image content =="
 
-function verify_io()
+verify_io()
 {
     if ($QEMU_IMG info -f "$IMGFMT" "$TEST_IMG" |
 	    grep "compat: 0.10" > /dev/null); then