gdb/testsuite: use clean_restart in gdb.server/server-run.exp

I think this sequence of commands can be replaced with clean_restart.

gdb/testsuite/ChangeLog:

	* gdb.server/server-run.exp: Use clean_restart.

Change-Id: If8c3eaa89f4ee58901282f5f1d5d4e1100ce7ac5

gdb/testsuite/ChangeLog

@@ -1,3 +1,7 @@
+2021-01-04  Simon Marchi  <simon.marchi@efficios.com>
+
+	* gdb.server/server-run.exp: Use clean_restart.
+
 2021-01-04  Simon Marchi  <simon.marchi@efficios.com>
 
 	* gdb.server/ext-run.exp: Use clean_restart.

gdb/testsuite/gdb.server/server-run.exp

@@ -29,16 +29,13 @@ if {[build_executable $testfile.exp $testfile $srcfile debug] == -1} {
     return -1
 }
 
-gdb_exit
-gdb_start
-gdb_load $binfile
+clean_restart $binfile
 
 # Make sure we're disconnected, in case we're testing with an
 # extended-remote board, therefore already connected.
 gdb_test "disconnect" ".*"
 
 gdbserver_run ""
-gdb_reinitialize_dir $srcdir/$subdir
 
 # We are now stopped at the program's entry point.  On targets which use
 # SVR4 dynamic linking, we should have automatically loaded symbols for