build: do not create versioned <xlator>.so files

There has been a misspelled option in the Makefile.am files. The option
is called -avoid-version, and not -avoidversion.

It is not trivial to provide a test-case for this. One way would be to
check generated RPMs with a command like this (output should be empty):

  $ rpm -qlp *.rpm | grep -E '/xlator/.+.so.0'

Change-Id: I2a6cc557eada4d098b73af5a254f8c75707543da
BUG: 1078365
Signed-off-by: Niels de Vos <ndevos@redhat.com>
Reviewed-on: http://review.gluster.org/7299
Reviewed-by: Lalatendu Mohanty <lmohanty@redhat.com>
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>