build: Remove --with-simulatorbin, replace with --enable-integration.

Bill recently integrated the tools integration tests into the test
harness and his approach assumes that the `tpm_server` binary is on the
PATH. This simplifies a few thing and generally it's just cleaner than
requiring the caller to pass the full path to the executable at
configure time.

This patch removes the --with-simulatorbin configure option replacing it
with the --enable-integration option instead. This option takes no
parameters but it does check that the 'tpm_server' binary is on the
callers path. Additionally this patch consolidates the multiple AC_IF
checks for the definition of the associated variable. The corresponding
option to the int-log-compiler.sh script is removed as well.

Signed-off-by: Philip Tricca <philip.b.tricca@intel.com>
diff --git a/.travis.yml b/.travis.yml
index 237a9aa..0942306 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -18,6 +18,7 @@
   - LD_LIBRARY_PATH="$(pwd)/cmocka/lib:/usr/lib"
   - CMOCKA_CFLAGS="-I$(pwd)/cmocka/include -I/usr/include"
   - CMOCKA_LIBS="-L$(pwd)/cmocka/lib -lcmocka"
+  - PATH="$(pwd)/ibmtpm/src:${PATH}"
 
 addons:
   apt:
@@ -84,7 +85,7 @@
     if [ "$CC" == "gcc" ]; then
       export CONFIGURE_OPTIONS="--enable-code-coverage";
     fi
-  - ../configure --enable-unit $CONFIGURE_OPTIONS --with-simulatorbin=$(pwd)/../ibmtpm/src/tpm_server
+  - ../configure --enable-unit --enable-integration $CONFIGURE_OPTIONS
   - make -j$(nproc) distcheck
   - make -j$(nproc) check
   - cat test-suite.log