Fix the initial sharding flaky test

[arindamnayak]

Fix for one more flaky test (which contains Too many connections error):

Error Trace:	base_sharding.go:151
        	            				base_sharding.go:351
        	            				base_sharding.go:323
        	            				sharding_util.go:495
        	Error:      	Expected nil, but got: &mysql.SQLError{Num:2012, State:"HY000", Message:"immediate error from server errorCode=1040 errorMsg=Too many connections", Query:""}
        	Test:       	TestInitialSharding

We were creating multiple connections in loop to insert and verify more than 2000 rows created by sharding test. This might be creating 'Too many connection' error. Now, the connection is created first and then passed around to insert/verify the rows

FYI @deepthi

Signed-off-by: Arindam Nayak [email protected]