clang compiler warnings: Fix format specified in framehook

This patch fixes an invalid format specifier used in the formatting of an
ERROR message in the framehook code. The format specifier specifies a
type of 'unsigned short', but the argument passed to it is of type 'int'.
The patch changes the format specifier to 'i'.

Review: https://reviewboard.asterisk.org/r/4540

ASTERISK-24917
Reported by: dkdegroot
patches:
  rb4535.patch submitted by dkdegroot (License 6600)
........

Merged revisions 434087 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/13@434088 65c4cc65-6c06-0410-ace0-fbb531ad65f3