t9110-git-svn-use-svm-props.sh: use the $( ... ) construct for command substitution

The Git CodingGuidelines prefer the $(...) construct for command
substitution instead of using the backquotes `...`.

The backquoted form is the traditional method for command
substitution, and is supported by POSIX.  However, all but the
simplest uses become complicated quickly.  In particular, embedded
command substitutions and/or the use of double quotes require
careful escaping with the backslash character.

The patch was generated by:

for _f in $(find . -name "*.sh")
do
	perl -i -pe 'BEGIN{undef $/;} s/`(.+?)`/\$(\1)/smg'  "${_f}"
done

and then carefully proof-read.

Signed-off-by: Elia Pinto <gitter.spiros@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t9110-git-svn-use-svm-props.sh

@@ -51,7 +51,7 @@ test_expect_success 'verify metadata for /dir' "
 
 test_expect_success 'find commit based on SVN revision number' "
         git svn find-rev r12 |
-	    grep `git rev-parse HEAD`
+	    grep $(git rev-parse HEAD)
         "
 
 test_expect_success 'empty rebase' "