read_sql routes sql query as table name snowflake-sqlalchemy
#### Code Sample
with [snowflake-sqlalchemy ](https://github.com/snowflakedb/snowflake-sqlalchemy) installed:

```python
from sqlalchemy import create_engine
import pandas as pd

CONN_STRING='snowflake://user:password@account/database'
engine=create_engine(CONN_STRING)

conn=engine.connect()
sql= 'SELECT COUNT(*) FROM "DATABASE_NAME"."SCHEMA_NAME"."TABLE_NAME"'
##this errors (stack below)
r=pd.read_sql(sql)

## this does not 
r=pd.read_sql_query(sql)

```
stack:
```
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.7/site-packages/pandas/io/sql.py", line 420, in read_sql
    pandas_sql.meta.reflect(only=[sql])
  File "/usr/local/lib/python3.7/site-packages/sqlalchemy/sql/schema.py", line 4261, in reflect
    "in %r%s: (%s)" % (bind.engine, s, ", ".join(missing))
sqlalchemy.exc.InvalidRequestError: Could not reflect: requested table(s) not available in Engine(snowflake://ethan:***@yxxxxxx.us-east-1/REDACTED_DB_NAME): (SELECT COUNT(*) FROM "REDACTED_DB_NAME"."REDACTED_DB_SCHEMA"."REDACTED_DB_TABLE")

```
#### Problem description
`read_sql` attempts to read sql queries as tables when running against snowflake. Calling `read_sql_query` is a workaround. 

looks like [this line](https://github.com/pandas-dev/pandas/blob/5c37a0b9caaed81ff3999d05b16be1303d184d77/pandas/io/sql.py#L415):
```
   try:
        _is_table_name = pandas_sql.has_table(sql)
    except Exception:
        # using generic exception to catch errors from sql drivers (GH24988)
        _is_table_name = False

```
is incorrectly determining statements to be table names. 

#### Expected Output
pd dataframe result of query.

#### Output of ``pd.show_versions()``
<details>
INSTALLED VERSIONS
------------------
commit           : None
python           : 3.7.6.final.0
python-bits      : 64
OS               : Linux
OS-release       : 4.19.76-linuxkit
machine          : x86_64
processor        : 
byteorder        : little
LC_ALL           : None
LANG             : C.UTF-8
LOCALE           : en_US.UTF-8

pandas           : 0.25.3
numpy            : 1.18.1
pytz             : 2019.3
dateutil         : 2.8.0
pip              : 19.3.1
setuptools       : 44.0.0
Cython           : None
pytest           : 5.3.0
hypothesis       : None
sphinx           : 2.3.1
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : None
html5lib         : None
pymysql          : None
psycopg2         : 2.8.4 (dt dec pq3 ext lo64)
jinja2           : 2.10.3
IPython          : None
pandas_datareader: None
bs4              : None
bottleneck       : None
fastparquet      : None
gcsfs            : None
lxml.etree       : None
matplotlib       : None
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : None
pytables         : None
s3fs             : None
scipy            : 1.4.1
sqlalchemy       : 1.3.12
tables           : None
xarray           : None
xlrd             : None
xlwt             : None
xlsxwriter       : None
</details>
