Set default GTEST_FILTER in android script

Merge from widevine repo of http://go/wvgerrit/14218

If GTEST_FILTER was not set, it defaults to "" which matches no
tests.  This CL changes it to "*" if it was "".

Also, quotes are added around the environment variable and command so
that it multiple variables can be set.

Change-Id: Icad9a1fbca2d1b436f6e37a2a080a70a384f0a1d

libwvdrmengine/run_all_unit_tests.sh

@@ -3,11 +3,15 @@
 final_result=0
 failed_tests=()
 
+if [ -z "$GTEST_FILTER" ]; then
+  GTEST_FILTER="*"
+fi
+
 # Execute a command in "adb shell" and capture the result.
 adb_shell_run() {
   local tmp_log="$OUT/mediadrmtest.log"
   local adb_error="[ADB SHELL] $@ failed"
-  adb shell GTEST_FILTER=$GTEST_FILTER $@ \|\| echo "$adb_error" | tee "$tmp_log"
+  adb shell "GTEST_FILTER=$GTEST_FILTER $@" \|\| echo "$adb_error" | tee "$tmp_log"
   ! grep -Fq "$adb_error" "$tmp_log"
   local result=$?
   if [ $result -ne 0 ]; then