qemu: Properly skip "char device redirected to" in QEMU log

When reading QEMU log for reporting it as an error message, we want to
skip "char device redirected to" line. However, this string is not
printed at the beginning of a line, which means STRPREFIX will never
find it.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NPavel Hrdina <phrdina@redhat.com>

src/qemu/qemu_process.c

@@ -1847,7 +1847,7 @@ qemuProcessReadLog(qemuDomainLogContextPtr logCtxt, char **msg)
     while ((eol = strchr(filter_next, '\n'))) {
         *eol = '\0';
         if (virLogProbablyLogMessage(filter_next) ||
-            STRPREFIX(filter_next, "char device redirected to")) {
+            strstr(filter_next, "char device redirected to")) {
             size_t skip = (eol + 1) - filter_next;
             memmove(filter_next, eol + 1, buf + got - eol);
             got -= skip;