RFR(xs) 8221621 FindTests.gmk cannot handle "=" in TEST.groups comments

[Ioi Lam]

https://bugs.openjdk.java.net/browse/JDK-8221621

The function FindJtregGroupsBody needs to filter out lines that starts 
with "#".

==================
diff -r 7d5a4a48e876 make/common/FindTests.gmk
--- a/make/common/FindTests.gmk    Wed Mar 27 14:40:36 2019 -0700
+++ b/make/common/FindTests.gmk    Thu Mar 28 09:59:19 2019 -0700
@@ -53,6 +53,7 @@
          -e 's/^groups\w*=//p' $1/TEST.ROOT)
      $1_JTREG_GROUP_FILES := $$(addprefix $1/, 
$$($1_JTREG_GROUP_FILENAMES))
      $1_JTREG_TEST_GROUPS := $$(strip $$(shell $$(SED) -n \
+        -e 's/^\#.*//g' \
          -e 's/\([^ ]*\)\w*=.*/\1/gp' $$(wildcard 
$$($1_JTREG_GROUP_FILES)) \
          | $$(SORT) -u))
    endif
==================

As a sanity check, I tested by adding $(error ${JTREG_TEST_GROUPS}) in 
this file to print out the groups that are found (on a clean repo 
without any "=" in comments). The output is identical with or without my 
change

Thanks
- Ioi