Removed forcing of color output in unit tests runner script.

tests/cta-valgrindUnitTests.sh.in

 #!/bin/bash
 # exit from the script on any error.
 set -e
-/usr/bin/cta-unitTests --gtest_color=yes
+/usr/bin/cta-unitTests
 
 valgrind --track-fds=yes --leak-check=full --demangle=yes --gen-suppressions=all --show-reachable=yes \
   --error-exitcode=1 --suppressions=/usr/share/cta-@CTA_VERSION@/unittest/valgrind.suppr              \
-  /usr/bin/cta-unitTests --gtest_color=yes 
+  /usr/bin/cta-unitTests
 
 valgrind --tool=helgrind -v --demangle=yes --gen-suppressions=all --conflict-cache-size=30000000      \
   --error-exitcode=1 --suppressions=/usr/share/cta-@CTA_VERSION@/unittest/helgrind.suppr              \
-  /usr/bin/cta-unitTests --gtest_color=yes
+  /usr/bin/cta-unitTests